Complete GORM to sqlc migration

- Remove GORM dependency, use sqlc for type-safe SQL queries
- Update all handlers to use sqlc patterns (context, value types)
- Fix N+1 query problem in domain listing with JOIN query
- Enable SQL query logging in debug mode (USE_EMBEDDED=false)
- Add comprehensive comments for non-Go developers

backend/cmd/server/main.go

@@ -3,6 +3,7 @@
 package main
 
 import (
+	"context"     // context for cancellation and timeouts
 	"crypto/rand" // cryptographically secure random number generator
 	"flag"        // standard library for parsing command-line flags
 	"fmt"         // formatted I/O, used here for printing output
@@ -90,25 +91,22 @@ func main() {
 			log.Fatalf("Failed to hash password: %v", err)
 		}
 
+		ctx := context.Background()
+
 		// Get or create a default domain for the admin user.
-		domains, err := database.GetAllDomains()
+		domains, err := database.GetAllDomains(ctx)
 		if err != nil || len(domains) == 0 {
 			// Create a default domain if none exist.
-			domain, err := database.CreateDomain("localhost")
+			err := database.CreateDomain(ctx, "localhost")
 			if err != nil {
 				log.Fatalf("Failed to create default domain: %v", err)
 			}
-			if err := database.UpsertAdminUser("admin", hash, domain.ID); err != nil {
-				log.Fatalf("Failed to reset admin password: %v", err)
+			domains, err = database.GetAllDomains(ctx)
+			if err != nil || len(domains) == 0 {
+				log.Fatalf("Failed to get domain: %v", err)
 			}
-			fmt.Printf("Admin password reset successfully.\n")
-			fmt.Printf("Username: admin\n")
-			fmt.Printf("Password: %s\n", password)
-			fmt.Printf("Default domain created: localhost\n")
-			return
 		}
-		// Use the first domain found.
-		if err := database.UpsertAdminUser("admin", hash, domains[0].ID); err != nil {
+		if err := database.UpsertAdminUser(ctx, "admin", hash, domains[0].ID); err != nil {
 			log.Fatalf("Failed to reset admin password: %v", err)
 		}
 		fmt.Printf("Admin password reset successfully.\n")