Refactor converters, add unit tests, and enhance CI workflows

.editorconfig

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+root = true
+
+[*]
+charset = utf-8
+end_of_line = crlf
+indent_style = space
+indent_size = 4
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.{cs,csx}]
+indent_size = 4
+dotnet_sort_system_directives_first = true
+dotnet_separate_import_directive_groups = false
+
+# C# code style
+csharp_new_line_before_open_brace = all
+csharp_new_line_before_else = true
+csharp_new_line_before_catch = true
+csharp_new_line_before_finally = true
+csharp_indent_case_contents = true
+csharp_indent_switch_labels = true
+csharp_space_after_cast = false
+csharp_space_after_keywords_in_control_flow_statements = true
+csharp_space_between_method_declaration_parameter_list_parentheses = false
+csharp_space_between_method_call_parameter_list_parentheses = false
+csharp_prefer_braces = true:suggestion
+csharp_style_var_for_built_in_types = false:suggestion
+csharp_style_var_when_type_is_apparent = true:suggestion
+csharp_style_var_elsewhere = false:suggestion
+csharp_style_expression_bodied_methods = false:silent
+csharp_style_expression_bodied_constructors = false:silent
+csharp_style_expression_bodied_properties = true:suggestion
+csharp_prefer_simple_using_statement = true:suggestion
+csharp_style_namespace_declarations = file_scoped:suggestion
+
+# Naming conventions
+dotnet_naming_style.pascal_case_style.capitalization = pascal_case
+dotnet_naming_style.camel_case_style.capitalization = camel_case
+dotnet_naming_style.underscore_camel_style.required_prefix = _
+dotnet_naming_style.underscore_camel_style.capitalization = camel_case
+
+dotnet_naming_rule.private_fields_should_be_underscore_camel.severity = suggestion
+dotnet_naming_rule.private_fields_should_be_underscore_camel.symbols = private_fields
+dotnet_naming_rule.private_fields_should_be_underscore_camel.style = underscore_camel_style
+
+dotnet_naming_symbols.private_fields.applicable_kinds = field
+dotnet_naming_symbols.private_fields.applicable_accessibilities = private
+
+[*.{xml,csproj,props,targets,config,nuspec}]
+indent_size = 2
+
+[*.{json,yaml,yml}]
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.{sh,bash}]
+end_of_line = lf
+
+[Makefile]
+indent_style = tab

.gitattributes

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+# Auto detect text files and perform LF normalization
+* text=auto eol=crlf
+
+# Source files
+*.cs     text eol=crlf diff=csharp
+*.vb     text eol=crlf
+*.csproj text eol=crlf
+*.sln    text eol=crlf
+*.props  text eol=crlf
+*.targets text eol=crlf
+*.config text eol=crlf
+*.json   text eol=crlf
+*.xml    text eol=crlf
+*.yaml   text eol=crlf
+*.yml    text eol=crlf
+*.md     text eol=crlf
+*.txt    text eol=crlf
+*.csv    text eol=crlf
+*.editorconfig text eol=crlf
+*.gitattributes text eol=crlf
+*.gitignore text eol=crlf
+
+# Shell scripts - keep LF
+*.sh     text eol=lf
+*.bash   text eol=lf
+
+# Binary files
+*.png    binary
+*.jpg    binary
+*.jpeg   binary
+*.gif    binary
+*.ico    binary
+*.pdf    binary
+*.docx   binary
+*.doc    binary
+*.xls    binary
+*.xlsx   binary
+*.zip    binary
+*.7z     binary
+*.gz     binary
+*.nupkg  binary
+*.snupkg binary
+*.dll    binary
+*.exe    binary
+*.pdb    binary

.github/WORKFLOWS.md

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+# GitHub Actions Workflows
+
+This repository uses GitHub Actions for CI/CD automation.
+
+## Workflows
+
+### 1. **CI** (`ci.yml`)
+Runs on every push and pull request to `develop` and `master` branches.
+- ✅ Builds the solution (.NET 9)
+- ✅ Runs all unit tests
+- ✅ Collects code coverage
+- ✅ Uploads test results as artifacts
+
+### 2. **CodeQL Security Scan** (`codeql.yml`)
+Runs on push, pull request, and weekly schedule (Monday 03:00 UTC).
+- 🔒 Analyzes C# code for security vulnerabilities
+- 🔍 Detects code quality issues
+- 📊 Uploads results to GitHub Security tab
+
+### 3. **Publish to NuGet** (`nuget-publish.yml`)
+Automatically publishes to NuGet.org when a new release is created.
+- 📦 Extracts version from release tag (e.g., `v1.8.0`)
+- 🔨 Builds and tests the library
+- 📤 Publishes to NuGet.org
+- 💾 Saves package as artifact
+
+## Setup Instructions
+
+### Required Secrets
+
+To enable NuGet publishing, add the following secret to your repository:
+
+1. Go to **Settings** → **Secrets and variables** → **Actions**
+2. Click **New repository secret**
+3. Add:
+   - **Name:** `NUGET_API_KEY`
+   - **Value:** Your NuGet API key from https://www.nuget.org/account/apikeys
+
+### Creating a Release
+
+To publish a new version to NuGet:
+
+1. Update version in `src/FileConversionLibrary/FileConversionLibrary.csproj`
+2. Commit and push changes
+3. Create a new release on GitHub:
+   ```bash
+   git tag v1.8.0
+   git push origin v1.8.0
+   ```
+4. Go to GitHub → **Releases** → **Draft a new release**
+5. Choose the tag `v1.8.0`
+6. Add release notes
+7. Click **Publish release**
+
+The `nuget-publish.yml` workflow will automatically:
+- Extract version from the tag
+- Build and test the project
+- Publish to NuGet.org
+
+### Manual Publishing
+
+You can also trigger publishing manually:
+
+1. Go to **Actions** → **Publish to NuGet**
+2. Click **Run workflow**
+3. Enter version (e.g., `1.8.0`)
+4. Click **Run workflow**
+
+## Status Badges
+
+Add these to your README.md:
+
+```markdown
+[![CI](https://github.com/TheMysteriousStranger90/FileConversionLibrary/actions/workflows/ci.yml/badge.svg)](https://github.com/TheMysteriousStranger90/FileConversionLibrary/actions/workflows/ci.yml)
+[![CodeQL](https://github.com/TheMysteriousStranger90/FileConversionLibrary/actions/workflows/codeql.yml/badge.svg)](https://github.com/TheMysteriousStranger90/FileConversionLibrary/actions/workflows/codeql.yml)
+[![NuGet](https://img.shields.io/nuget/v/FileConversionLibrary.svg)](https://www.nuget.org/packages/FileConversionLibrary/)
+```
+
+## Requirements
+
+- **.NET 9.0** SDK
+- **Ubuntu latest** runner
+- **NuGet API Key** (for publishing)

.github/workflows/ci.yml

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+name: CI
+
+on:
+  push:
+    branches: [ develop, master ]
+  pull_request:
+    branches: [ develop, master ]
+
+jobs:
+  build-and-test:
+    name: Build & Test (.NET 9)
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup .NET 9
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+
+      - name: Restore dependencies
+        run: dotnet restore FileConversionLibrary.sln
+
+      - name: Build (Release)
+        run: dotnet build FileConversionLibrary.sln -c Release --no-restore
+
+      - name: Run unit tests
+        run: |
+          dotnet test FileConversionLibrary.sln \
+            -c Release \
+            --no-build \
+            --logger "trx;LogFileName=test-results.trx" \
+            --results-directory ./TestResults \
+            --collect:"XPlat Code Coverage" \
+            -- DataCollectionRunSettings.DataCollectors.DataCollector.Configuration.Format=opencover
+
+      - name: Upload test results
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: test-results
+          path: ./TestResults/*.trx
+          retention-days: 30
+
+      - name: Upload coverage reports
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-reports
+          path: ./TestResults/**/coverage.opencover.xml
+          retention-days: 30
+
+      - name: Build summary
+        if: always()
+        run: |
+          echo "### Build Summary :rocket:" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "- **Branch:** ${{ github.ref_name }}" >> $GITHUB_STEP_SUMMARY
+          echo "- **Commit:** ${{ github.sha }}" >> $GITHUB_STEP_SUMMARY
+          echo "- **.NET Version:** 9.0" >> $GITHUB_STEP_SUMMARY
+          echo "- **Status:** ${{ job.status }}" >> $GITHUB_STEP_SUMMARY

.github/workflows/codeql.yml

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+name: CodeQL Security Scan
+
+on:
+  push:
+    branches: [ develop, master ]
+  pull_request:
+    branches: [ develop, master ]
+  schedule:
+    # Run weekly on Monday at 03:00 UTC
+    - cron: '0 3 * * 1'
+
+jobs:
+  analyze:
+    name: Analyze (C#)
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    permissions:
+      security-events: write
+      actions: read
+      contents: read
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup .NET 9
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '9.0.x'
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: csharp
+          queries: security-and-quality
+
+      - name: Restore dependencies
+        run: dotnet restore FileConversionLibrary.sln
+
+      - name: Build for CodeQL analysis
+        run: dotnet build FileConversionLibrary.sln -c Release --no-restore
+
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:csharp"
+
+      - name: Security scan summary
+        if: always()
+        run: |
+          echo "### Security Scan Summary :shield:" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "- **Language:** C#" >> $GITHUB_STEP_SUMMARY
+          echo "- **Status:** ${{ job.status }}" >> $GITHUB_STEP_SUMMARY
+          echo "- **Scan Date:** $(date -u +''%Y-%m-%d %H:%M UTC'')" >> $GITHUB_STEP_SUMMARY