perf(frontend): add build.rs asset pipeline with oxc + lightningcss

- Bundle 31 JS files → single app.{hash}.js (oxc minifier)
- Bundle 36 CSS files → single app.{hash}.css (lightningcss)
- Resolve CSS @import chains at build time
- Inline theme-init.js to eliminate render-blocking script
- Minify all individual JS/CSS/JSON assets in static-dist/
- Auto-update Service Worker cache manifest with bundle hashes
- FNV hash-based cache-busting filenames

Results: 88 → 12 requests, 640 kB → 96.5 kB transferred (-85%)

Build modes:
- Debug: copies HTML to OUT_DIR, serves original static/
- Release: generates static-dist/ with processed assets

Also:
- Update Dockerfile to include build.rs in cacher stage
- Serve static-dist/ in release Docker builds
- Remove host static/ bind mount from docker-compose
- Switch include_str!() to OUT_DIR for all HTML pages

.gitignore

@@ -2,6 +2,9 @@
 /target/
 **/target/
 
+# Processed static assets (generated by build.rs in release mode)
+/static-dist/
+
 # Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
 # More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
 # Cargo.lock