feat: add Docker Compose deployment and serve assets via StaticFS

Embed full assets directory and serve with via's StaticFS instead of a
custom HTTP handler. Move SQLite DB to data/c4.db for clean volume
mounting. Add multi-stage Dockerfile, docker-compose.yml, and
.dockerignore.

docker-compose.yml

@@ -0,0 +1,17 @@
+services:
+  c4:
+    build: .
+    container_name: c4
+    restart: unless-stopped
+    ports:
+      - "8080:8080"
+    env_file:
+      - path: .env
+        required: false
+    environment:
+      - PORT=8080
+    volumes:
+      - c4-data:/app/data
+
+volumes:
+  c4-data: