fix(ci): use build:frontend in CI build job

The Build job was running `pnpm build` (tauri build) which requires
Linux dependencies. Changed to `pnpm build:frontend` (vite build only)
since Rust is already tested by separate jobs.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: fazxes

.github/workflows/ci.yml

@@ -77,7 +77,7 @@ jobs:
           node-version: ${{ env.NODE_VERSION }}
           cache: 'pnpm'
       - run: pnpm install --frozen-lockfile
-      - run: pnpm build
+      - run: pnpm build:frontend
 
       # Only upload artifacts on main branch to save storage
       # continue-on-error prevents storage quota issues from failing the build