feat: add proper HTTP status codes to all API error responses

- 217 error returns across 18 route files + api.py now use JSONResponse
  with appropriate HTTP status codes instead of returning HTTP 200
- Status code distribution: 500 (121), 400 (39), 503 (28), 404 (24), 409 (3), 502 (2)
- Fixed language.py tuple-return bug (was serializing as JSON array)
- Fixed bare except clauses in bipolar_mode.py and voice.py
- Body-level error schemas preserved (status/error + success/error patterns)
  so web UI continues working without changes
- chat.py (SSE) unchanged: errors sent within stream protocol
- All 170 tests pass

bot/routes/bot_actions.py

@@ -1,6 +1,7 @@
 """Core bot action routes: conversation reset, sleep, wake, bedtime."""
 
 from fastapi import APIRouter
+from fastapi.responses import JSONResponse
 import globals
 from commands.actions import (
     force_sleep,
@@ -49,4 +50,4 @@ async def bedtime_endpoint(guild_id: int = None):
             globals.client.loop.create_task(send_bedtime_now())
             return {"status": "ok", "message": "Bedtime reminder queued for all servers"}
     else:
-        return {"status": "error", "message": "Bot not ready"}
+        return JSONResponse(status_code=503, content={"status": "error", "message": "Bot not ready"})