feat(settings): add DevTools-style config tabs with autosave

[AugustoL]

Description

Reorganize the Settings page into DevTools-style tabs (Network, Providers, Display, Advanced) with deep-linkable tab state via query params, debounced auto-save for most tabs, and explicit manual save for the Providers tab.

Re-applies #304 (which was merged to main and reverted), now targeting dev.

Related Issue

Closes #292
Closes #297

Type of Change

• New feature
• Refactoring

Changes Made

• Split the Settings page into 4 tabs: Network, Providers, Display, Advanced
• Added deep-linkable tab state via ?tab= query param, persisted to localStorage
• Replaced manual save flow with debounced auto-save (450ms) + inline save status pill
• Providers tab uses explicit save button to avoid auto-save loops while typing API keys
• Mobile-friendly tab selector layout
• Normalized URL handling to avoid duplicate hash fragments

Screenshots (if applicable)

N/A

Checklist

• I have run npm run format:fix and npm run lint:fix
• I have run npm run typecheck with no errors
• I have run tests with npm run test:run
• I have tested my changes locally
• I have updated documentation if needed
• My code follows the project's architecture patterns

Additional Notes

Cherry-picked from the original PR #304 commits with conflict resolution for changes that landed on dev since.

[github-actions]

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📝 Commit: 60d0cf82b62e58888b2d149d166b4797db872f64