fix(nix): drop inherited source patch

[vimoppa]

What Changed

• Clear nixpkgs’ source-specific postPatch after replacing the package source with this repository.
• Keep the moving main source buildable when upstream changes apps/web/vite.config.ts.

Why

The package overrides nixpkgs’ pinned T3Code source but was still inheriting a patch written for that pinned revision. After the Vite host setup changed on main, substituteInPlace --replace-fail no longer matched and every Nix build stopped during patchPhase.

The inherited patch only changes development-server host fallback behavior and is not required for the packaged desktop build. An empty override is required here; deleting the override would restore the stale inherited hook.

Validation

• nix build .#t3code --no-link --max-jobs 1
• Confirmed the packaged app bundle and executable exist
• plutil -lint on the packaged Info.plist
• git diff --check

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes (not applicable)
• I included a video for animation/interaction changes (not applicable)