Extract settings page navigation config

[ichwars]

Summary

• move static settings headers, sub-tab metadata, legacy routing maps, and URL resolver helpers into settings-page-config.ts
• reduce SettingsPage.tsx from 7,618 to 7,074 lines without changing page state or rendered settings content
• lower the source-size allowlist ceiling to the exact new size; the extracted module is 610 lines and below budget

Local verification

• npm.cmd exec -- tsc -b
• npm.cmd run lint
• SettingsPage and settingsNavigation tests: 116 passed
• full frontend suite: 244 files / 2,848 tests passed
• all 11 locales in parity
• isolated Vite production build: 3,045 modules transformed
• source size budget: 1,573 files passed
• source budget unit tests: 14 passed