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

src/interfaces/nextcloud/login_v2_handler.rs

@@ -135,7 +135,10 @@ pub async fn handle_login_page(
         return StatusCode::NOT_FOUND.into_response();
     }
 
-    html_with_csp(include_str!("../../../static/nextcloud-login.html"))
+    html_with_csp(include_str!(concat!(
+        env!("OUT_DIR"),
+        "/nextcloud-login.html"
+    )))
 }
 
 pub async fn handle_login_submit(