feat(api): use Tencent ASR flash with 16k_zh_large and dev transcript logs

Replace CreateRecTask polling with recording-file flash API, add TENCENT_APP_ID,
remove server-side pydub slicing, and log ASR recognition text at INFO in development.

Co-authored-by: Cursor <cursoragent@cursor.com>

api/app/core/app_config_models.py

@@ -205,6 +205,7 @@ class AsrConfig(BaseModel):
 
     provider: Literal["tencent"] = "tencent"
     engine_type: Literal["16k_zh_large"] = "16k_zh_large"
+    request_timeout_seconds: float = 60.0
 
 
 class TtsConfig(BaseModel):