feat: add Cloudflare AI TTS engine (aura-2-en) with voice grouping in UI

backend/internal/config/config.go

@@ -66,6 +66,18 @@ type PocketTTS struct {
 	URL string
 }
 
+// CFAI holds credentials for Cloudflare Workers AI TTS.
+type CFAI struct {
+	// AccountID is the Cloudflare account ID.
+	// An empty string disables CF AI generation.
+	AccountID string
+	// APIToken is a Workers AI API token with Workers AI Read+Edit permissions.
+	APIToken string
+	// Model is the Workers AI TTS model ID.
+	// Defaults to "@cf/deepgram/aura-2-en" when empty.
+	Model string
+}
+
 // LibreTranslate holds connection settings for a self-hosted LibreTranslate instance.
 type LibreTranslate struct {
 	// URL is the base URL of the LibreTranslate instance, e.g. https://translate.libnovel.cc
@@ -153,6 +165,7 @@ type Config struct {
 	MinIO          MinIO
 	Kokoro         Kokoro
 	PocketTTS      PocketTTS
+	CFAI           CFAI
 	LibreTranslate LibreTranslate
 	HTTP           HTTP
 	Runner         Runner
@@ -203,6 +216,12 @@ func Load() Config {
 			URL: envOr("POCKET_TTS_URL", ""),
 		},
 
+		CFAI: CFAI{
+			AccountID: envOr("CFAI_ACCOUNT_ID", ""),
+			APIToken:  envOr("CFAI_API_TOKEN", ""),
+			Model:     envOr("CFAI_TTS_MODEL", ""),
+		},
+
 		LibreTranslate: LibreTranslate{
 			URL:    envOr("LIBRETRANSLATE_URL", ""),
 			APIKey: envOr("LIBRETRANSLATE_API_KEY", ""),