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/__main__.py

@@ -0,0 +1,24 @@
+import speech_recognition as sr
+
+r = sr.Recognizer()
+m = sr.Microphone()
+
+try:
+    print("A moment of silence, please...")
+    with m as source: r.adjust_for_ambient_noise(source)
+    print("Set minimum energy threshold to {}".format(r.energy_threshold))
+    while True:
+        print("Say something!")
+        with m as source: audio = r.listen(source)
+        print("Got it! Now to recognize it...")
+        try:
+            # recognize speech using Google Speech Recognition
+            value = r.recognize_google(audio)
+
+            print("You said {}".format(value))
+        except sr.UnknownValueError:
+            print("Oops! Didn't catch that")
+        except sr.RequestError as e:
+            print("Uh oh! Couldn't request results from Google Speech Recognition service; {0}".format(e))
+except KeyboardInterrupt:
+    pass