feat(auth): add credential batch management

[TWJohnJohn20116]

Summary

• add multi-select controls to the authentication-file list, including select/deselect visible results
• add batch enable, disable, and delete actions with accurate action counts
• preserve selections across filters, prune stale selections after refresh, and skip runtime-only credentials during deletion
• report partial failures per credential and add responsive styles plus localized strings
• cover batch target selection rules with unit tests

Testing

• bun run check
• bun test (114 passed)
• bun run build
• cargo test --manifest-path src-tauri/Cargo.toml (202 passed)