analyse: thread user.lang into the system prompt

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/routers/universe.py

@@ -36,7 +36,7 @@ from fastapi.responses import JSONResponse
 from sqlalchemy import and_, func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from app.auth import require_auth
+from app.auth import CurrentUser, require_auth
 from app.config import get_settings
 from app.db import get_session, utcnow
 from app.logging import get_logger
@@ -341,10 +341,11 @@ async def parse_portfolio(
 # ---------------------------------------------------------------------------
 
 
-@router.post("/analyze", dependencies=[Depends(require_paid)])
+@router.post("/analyze")
 async def analyze_portfolio(
     request: Request,
     session: AsyncSession = Depends(get_session),
+    principal: CurrentUser = Depends(require_paid),
 ) -> dict:
     """Generate AI commentary for the supplied pie. The pie is held in
     memory only for the duration of the LLM call; nothing about holdings
@@ -364,6 +365,11 @@ async def analyze_portfolio(
     except Exception:
         raise HTTPException(status_code=400, detail="malformed JSON body")
 
+    user_lang = (
+        principal.user.lang if (principal.user and principal.user.lang) else "en"
+    )
+    payload["lang"] = user_lang
+
     try:
         req = portfolio_analysis.parse_request(payload)
     except ValueError as e: