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.

cli/serve.go

@@ -0,0 +1,36 @@
+package cli
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+
+	"github.com/spf13/cobra"
+	"yoink/web"
+)
+
+var serveCmd = &cobra.Command{
+	Use:   "serve",
+	Short: "Start the Yoink web UI",
+	Args:  cobra.NoArgs,
+	Run: func(cmd *cobra.Command, args []string) {
+		library, ok := os.LookupEnv("YOINK_LIBRARY")
+		if !ok {
+			userHome, _ := os.UserHomeDir()
+			library = filepath.Join(userHome, ".yoink")
+		}
+
+		port, _ := cmd.Flags().GetString("port")
+		addr := fmt.Sprintf(":%s", port)
+
+		if err := web.Listen(addr, library); err != nil {
+			log.Fatal(err)
+		}
+	},
+}
+
+func init() {
+	serveCmd.Flags().StringP("port", "p", "8080", "Port to listen on")
+	cli.AddCommand(serveCmd)
+}