Rename project module and database references: Bookmann → Bookhoard

Core infrastructure changes:
- Update Go module name: bookmann → bookhoard
- Rename database schema references and comments
- Update database column names: bookmann_uuid → bookhoard_uuid
- Rename SQL query functions: GetDeviceCatalogByBookmannUUID → GetDeviceCatalogByBookhoardUUID
- Update configuration defaults

This is part 1 of the project rename to Bookhoard.

internal/config/config.go

@@ -30,7 +30,7 @@ func LoadConfig() *Config {
 		DatabasePort:      getEnv("DATABASE_PORT", "5432"),
 		DatabaseUser:      getEnv("DATABASE_USER", "postgres"),
 		DatabasePassword:  getEnv("DATABASE_PASSWORD", "password"),
-		DatabaseName:      getEnv("DATABASE_NAME", "bookmann"),
+		DatabaseName:      getEnv("DATABASE_NAME", "bookhoard"),
 		JWTSecret:         getEnv("JWT_SECRET", "your-secret-key"),
 		UploadPath:        getEnv("UPLOAD_PATH", "./uploads"),
 		TestMode:          getEnvBool("TEST_MODE", false),