feat(voice): transcribe Telegram voice notes with SpeechRecognition

Add a voice message handler that downloads OGG audio, converts it to
WAV via pydub/ffmpeg, and transcribes it with Google Speech Recognition
(pt-BR) before feeding the text into the normal message pipeline.

Also extract shared text processing into process_text_message, guard
against updates without a text attribute, switch the default AI provider
to openrouter with deepseek-v4-flash, and document the ffmpeg system
requirement in DEPLOY.md.

venv/lib/python3.11/site-packages/speech_recognition/exceptions.py

@@ -0,0 +1,22 @@
+class SetupError(Exception):
+    pass
+
+
+class WaitTimeoutError(Exception):
+    pass
+
+
+class RequestError(Exception):
+    pass
+
+
+class UnknownValueError(Exception):
+    pass
+
+
+class TranscriptionNotReady(Exception):
+    pass
+
+
+class TranscriptionFailed(Exception):
+    pass