Fix project icon syncing and fallbacks

[hoomanaskari]

Summary

This PR fixes project icon behavior so custom icons set in project settings propagate across the app and fallback avatars behave consistently.

Root Cause

• Some parts of the renderer were holding stale selected-project snapshots, so icon changes made in settings did not propagate back to the active workspace UI.
• Custom icons were being loaded through raw file:// URLs, which made icons stored under the app userData path render unreliably.
• Project rendering still fell back to GitHub avatars, which made local project identity inconsistent and ignored explicit custom project icon choices.

What Changed

• Added a selected-project normalization helper so the main UI rehydrates from the latest project records.
• Updated project settings mutations to sync the project cache and selected-project state immediately after rename, upload, removal, and delete actions.
• Switched custom project icon loading to the existing binary file reader and versioned icon cache keys with updatedAt so new uploads replace old cached icons cleanly.
• Replaced GitHub avatar fallback with a repo-initial fallback avatar in the shared project icon component.
• Reused the shared project icon rendering path across the settings preview, project selector, sidebar, archive popover, quick switch surfaces, and drafts.
• Increased sidebar icon size and added subtle bordered styling for fallback avatars.

Impact

• Custom project icons now stay in sync after being changed in settings.
• Projects without a custom icon now use a predictable repo-initial fallback instead of a GitHub avatar.
• Sidebar and project-picker surfaces render project identity more consistently.

Validation

• Ran bun run dev successfully.
• Manually verified the icon flow locally:
  • upload a custom icon from project settings
  • confirm it appears in the settings preview, project selector, sidebar, and compose area
  • remove the custom icon and confirm the UI falls back to the repo-initial avatar instead of a GitHub avatar