feat(web): add dockerized web UI with comic library browser

Adds a `yoink serve` command that starts an HTTP server with a
Sonarr/MeTube-inspired dark UI. Features a URL input bar for
triggering downloads, a 150x300 cover grid with filter and sort
controls, a live download queue strip, and toast notifications.

Includes Dockerfile (multi-stage, distroless runtime) and
docker-compose.yml for easy deployment.

docker-compose.yml

@@ -0,0 +1,10 @@
+services:
+  yoink:
+    build: .
+    ports:
+      - "8080:8080"
+    volumes:
+      - ./library:/library
+    environment:
+      - YOINK_LIBRARY=/library
+    restart: unless-stopped