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/figurines.py

@@ -1,6 +1,7 @@
 """Figurine subscriber and send routes."""
 
 from fastapi import APIRouter, Form
+from fastapi.responses import JSONResponse
 import globals
 from utils.figurine_notifier import (
     load_subscribers as figurine_load_subscribers,
@@ -29,7 +30,7 @@ async def add_figurine_subscriber(user_id: str = Form(...)):
         ok = figurine_add_subscriber(uid)
         return {"status": "ok", "added": ok}
     except Exception as e:
-        return {"status": "error", "message": str(e)}
+        return JSONResponse(status_code=500, content={"status": "error", "message": str(e)})
 
 
 @router.delete("/figurines/subscribers/{user_id}")
@@ -39,7 +40,7 @@ async def delete_figurine_subscriber(user_id: str):
         ok = figurine_remove_subscriber(uid)
         return {"status": "ok", "removed": ok}
     except Exception as e:
-        return {"status": "error", "message": str(e)}
+        return JSONResponse(status_code=500, content={"status": "error", "message": str(e)})
 
 
 @router.post("/figurines/send_now")
@@ -49,7 +50,7 @@ async def figurines_send_now(tweet_url: str = Form(None)):
         logger.info(f"Sending figurine DMs to all subscribers, tweet_url: {tweet_url}")
         globals.client.loop.create_task(send_figurine_dm_to_all_subscribers(globals.client, tweet_url=tweet_url))
         return {"status": "ok", "message": "Figurine DMs queued"}
-    return {"status": "error", "message": "Bot not ready"}
+    return JSONResponse(status_code=503, content={"status": "error", "message": "Bot not ready"})
 
 
 @router.post("/figurines/send_to_user")
@@ -59,14 +60,14 @@ async def figurines_send_to_user(user_id: str = Form(...), tweet_url: str = Form
 
     if not globals.client or not globals.client.loop or not globals.client.loop.is_running():
         logger.error("Bot not ready")
-        return {"status": "error", "message": "Bot not ready"}
+        return JSONResponse(status_code=503, content={"status": "error", "message": "Bot not ready"})
 
     try:
         user_id_int = int(user_id)
         logger.debug(f"Parsed user_id as {user_id_int}")
     except ValueError:
         logger.error(f"Invalid user ID: '{user_id}'")
-        return {"status": "error", "message": "Invalid user ID"}
+        return JSONResponse(status_code=400, content={"status": "error", "message": "Invalid user ID"})
 
     # Clean up tweet URL if it's empty string
     if tweet_url == "":