feat: Phase 2 — database layer

- PostgreSQL schema: sources, manga, chapters, pages, source_meta with indexes
- golang-migrate runner with embedded SQL via go:embed (pgx5:// scheme)
- sqlc-generated type-safe queries for all tables (pgx/v5 native)
- Config package with all env vars including TTL durations
- Wire DB init and config into cmd/server/main.go

cmd/server/main.go

@@ -1,22 +1,33 @@
 package main
 
 import (
+	"context"
 	"fmt"
 	"log"
 	"net/http"
 
-	_ "goyomi/internal/registry" // ensures registry package is initialized
+	"goyomi/internal/config"
+	"goyomi/internal/db"
+	_ "goyomi/internal/registry"
 )
 
 func main() {
+	cfg := config.Load()
+
+	ctx := context.Background()
+	database, err := db.Open(ctx)
+	if err != nil {
+		log.Fatalf("db: %v", err)
+	}
+	defer database.Close()
+
 	mux := http.NewServeMux()
 	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintln(w, "ok")
 	})
 
-	addr := ":8080"
-	log.Printf("listening on %s", addr)
-	if err := http.ListenAndServe(addr, mux); err != nil {
+	log.Printf("listening on %s", cfg.Addr)
+	if err := http.ListenAndServe(cfg.Addr, mux); err != nil {
 		log.Fatal(err)
 	}
 }