Apply conversation bot improvements (proto-improvements)

Diff vs working-copy baseline = exactly this session's bot edits:
- constants.py: env-var config, safe JSON loading, optional-dependency
  guards, env->netrc token resolution, API_SHARED_KEY + service_headers()
- communication_subroutine.py: queue get(timeout) + Empty handling,
  daemon threads, cooperative stop_event, inbound _authorize_request()
- bot.py: single asyncio event loop with cooperative shutdown
- music_functions / radio_commands / librarian_commands: send
  X-Conjurer-Api-Key on internal HTTP calls via service_headers()

Musician runtime data overlay dropped; conjurer_musician/.gitignore now
keeps generated playlists/mp3 out of the repo. The 1+2+3 musician code
port already lives in the base conjurer_musician.

Depends on #9: must merge after restructure/working-copy-root.

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

radio_commands.py

@@ -8,7 +8,9 @@ import uuid
 
 import asyncio
 from datetime import datetime
-from constants import RADIO_HARBOR_ADDRESS, SKIP_TRACK, FILE_SERVICE_ADDRESS, ADD_TO_PRIO_PLAYLIST, REQUEST_MUSIC, CREATE_PRIO_PLAYLIST, CLEAR_PRIO
+from constants import RADIO_HARBOR_ADDRESS, SKIP_TRACK, FILE_SERVICE_ADDRESS, ADD_TO_PRIO_PLAYLIST, REQUEST_MUSIC, CREATE_PRIO_PLAYLIST, CLEAR_PRIO, service_headers
+
+SERVICE_HEADERS = service_headers()
 
 class RadioModule(commands.Cog):
     def __init__(self, bot, logger_name):
@@ -34,6 +36,7 @@ class RadioModule(commands.Cog):
                 coroutine = asyncio.to_thread(
                     requests.get,
                     f"{RADIO_HARBOR_ADDRESS}{SKIP_TRACK}",
+                    headers=SERVICE_HEADERS,
                     timeout=360,
                 )
                 result = await coroutine
@@ -95,6 +98,7 @@ class RadioModule(commands.Cog):
                 requests.post,
                 f"{FILE_SERVICE_ADDRESS}{ADD_TO_PRIO_PLAYLIST}",
                 json=jrequest,
+                headers=SERVICE_HEADERS,
                 timeout=360,
             )
             result = await coroutine
@@ -130,6 +134,7 @@ class RadioModule(commands.Cog):
                 requests.post,
                 f"{FILE_SERVICE_ADDRESS}{REQUEST_MUSIC}",
                 json=jrequest,
+                headers=SERVICE_HEADERS,
                 timeout=360,
             )
             result = await coroutine
@@ -167,6 +172,7 @@ class RadioModule(commands.Cog):
                 requests.post,
                 f"{FILE_SERVICE_ADDRESS}{CREATE_PRIO_PLAYLIST}",
                 json=jrequest,
+                headers=SERVICE_HEADERS,
                 timeout=360,
             )
             result = await coroutine
@@ -194,6 +200,7 @@ class RadioModule(commands.Cog):
             coroutine = asyncio.to_thread(
                 requests.get,
                 f"{FILE_SERVICE_ADDRESS}{CLEAR_PRIO}",
+                headers=SERVICE_HEADERS,
                 timeout=360,
             )
             result = await coroutine