fix: voice_recognition uses constants for credentials and paths

The cog did its own netrc read from a hardcoded /home/pi/.netrc at import
time, crashing on any other host. Now:

- constants.py: ASSEMBLYAI_API_KEY resolved like every other token
  (env ASSEMBLYAI_API_KEY -> netrc machine 'assemblyai' at
  CONJURER_NETRC_FILE); new TRANSCRIPTS_PATH (env
  CONJURER_TRANSCRIPTS_PATH, defaults next to the log file, created by the
  runtime layout)
- voice_recognition_commands.py: drop the hardcoded netrc read and
  transcript dir; when the key is missing raise a clear RuntimeError so
  the guarded loader disables ONLY this cog with a readable reason
- bot.env.example: document ASSEMBLYAI_API_KEY

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

voice_recognition_commands.py

@@ -1,6 +1,5 @@
 import asyncio
 import logging
-import netrc
 import time
 import wave
 
@@ -9,11 +8,17 @@ import discord
 from discord.ext import commands, tasks, voice_recv
 from discord.opus import Decoder as OpusDecoder
 
-# Replace with your API key
-NETRC_FILE = "/home/pi/.netrc"
-netrc_mod = netrc.netrc(NETRC_FILE)
-authTokens = netrc_mod.authenticators("assemblyai")
-aai.settings.api_key = authTokens[2]
+from constants import ASSEMBLYAI_API_KEY, TRANSCRIPTS_PATH
+
+# Credentials come from constants (env ASSEMBLYAI_API_KEY, or the 'assemblyai'
+# machine in the netrc at CONJURER_NETRC_FILE). Raising here means the guarded
+# extension loader logs the reason and disables ONLY this cog.
+if not ASSEMBLYAI_API_KEY:
+    raise RuntimeError(
+        "AssemblyAI API key not configured (netrc machine 'assemblyai' or "
+        "ASSEMBLYAI_API_KEY env) - voice recognition stays disabled"
+    )
+aai.settings.api_key = ASSEMBLYAI_API_KEY
 
 discord.opus._load_default()
 CHANNELS = OpusDecoder.CHANNELS
@@ -23,7 +28,7 @@ SAMPLING_RATE = OpusDecoder.SAMPLING_RATE
 # rotate file after there is 0.5s between last received pcm for user.
 # delete messsages after user disconnect
 
-LOCATION = "/home/pi/Conjurer/transcripts/"
+LOCATION = TRANSCRIPTS_PATH
 
 
 class CommunicationObject: