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/tests/test_default_toml_legacy_parity.py

@@ -18,5 +18,6 @@ def test_default_toml_matches_legacy_settings_defaults() -> None:
 
     assert cfg.asr.provider == "tencent"
     assert cfg.asr.engine_type == "16k_zh_large"
+    assert cfg.asr.request_timeout_seconds == 60.0
 
     assert cfg.misc.tencent_sms_template_param_count == 2