refactor: Improve code readability and structure across TTS modules

app/services/tts/providers/gtts.py

@@ -2,11 +2,10 @@
 
 import asyncio
 import io
-from typing import Any
 
 from gtts import gTTS
 
-from ..base import TTSProvider
+from app.services.tts.base import TTSProvider
 
 
 class GTTSProvider(TTSProvider):
@@ -22,7 +21,7 @@ class GTTSProvider(TTSProvider):
         """Return the default file extension for this provider."""
         return "mp3"
 
-    async def generate_speech(self, text: str, **options: Any) -> bytes:
+    async def generate_speech(self, text: str, **options: str | bool | float) -> bytes:
         """Generate speech from text using Google TTS.
 
         Args:
@@ -38,7 +37,7 @@ class GTTSProvider(TTSProvider):
         slow = options.get("slow", False)
 
         # Run TTS generation in thread pool since gTTS is synchronous
-        def _generate():
+        def _generate() -> bytes:
             tts = gTTS(text=text, lang=lang, tld=tld, slow=slow)
             fp = io.BytesIO()
             tts.write_to_fp(fp)
@@ -64,7 +63,7 @@ class GTTSProvider(TTSProvider):
             "vi", "yo", "zh", "zh-cn", "zh-tw", "zu",
         ]
 
-    def get_option_schema(self) -> dict[str, Any]:
+    def get_option_schema(self) -> dict[str, dict[str, str | list[str] | bool]]:
         """Return schema for GTTS-specific options."""
         return {
             "lang": {