Add self-hosted RCS backend, extension, and ops tooling

Ship the Go/SQLite API and Web UI, Chrome/Brave capture addon,
Docker Compose, Pangolin reverse-proxy support, and a user-crontab
watchdog so the binary stays running without systemd.

backend/cmd/rcs/main.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+
+	"github.com/squid/rcs/backend/internal/api"
+	"github.com/squid/rcs/backend/internal/config"
+	"github.com/squid/rcs/backend/internal/db"
+	"github.com/squid/rcs/backend/internal/imgur"
+	"github.com/squid/rcs/backend/internal/web"
+)
+
+func main() {
+	cfg := config.Load()
+
+	if err := os.MkdirAll(cfg.ScreenshotDir, 0o755); err != nil {
+		log.Fatalf("create screenshot dir: %v", err)
+	}
+	if err := os.MkdirAll(filepath.Dir(cfg.DBPath), 0o755); err != nil {
+		log.Fatalf("create db dir: %v", err)
+	}
+
+	store, err := db.Open(cfg.DBPath)
+	if err != nil {
+		log.Fatalf("open db: %v", err)
+	}
+	defer store.Close()
+
+	imgurClient := imgur.New(cfg.ImgurClientID)
+	webUI, err := web.New(cfg, store, imgurClient)
+	if err != nil {
+		log.Fatalf("web ui: %v", err)
+	}
+
+	server := api.New(cfg, store, imgurClient, webUI)
+
+	fmt.Printf("RCS backend listening on http://%s\n", cfg.Addr)
+	fmt.Printf("  data dir: %s\n", cfg.DataDir)
+	fmt.Printf("  db:       %s\n", cfg.DBPath)
+	if cfg.PublicBaseURL != "" {
+		fmt.Printf("  public:   %s\n", cfg.PublicBaseURL)
+	}
+	if cfg.TrustProxy {
+		fmt.Println("  proxy:    trusting X-Forwarded-* headers")
+	}
+	if cfg.APIKey != "" {
+		fmt.Println("  api key:  enabled")
+	} else {
+		fmt.Println("  api key:  disabled (open)")
+	}
+	if imgurClient.Enabled() {
+		fmt.Println("  imgur:    enabled")
+	} else {
+		fmt.Println("  imgur:    disabled (set IMGUR_CLIENT_ID)")
+	}
+
+	if err := http.ListenAndServe(cfg.Addr, server.Handler()); err != nil {
+		log.Fatal(err)
+	}
+}