backend: dedupe shared logic (indicator_summary_job, CHAT_REFERENCE_LINE, call_openrouter alias)

- indicator_summary_job.py imported its own copies of _month_spend and
  _latest_quotes_by_group; _market_context.py already exposes these.
  Switched to the canonical imports. Also fixed _market_context's
  latest_quotes_by_group to actually filter null prices (it claimed to
  in its docstring but lacked the WHERE clause).
- api.py duplicated REFERENCE_LINE as CHAT_REFERENCE_LINE — same string,
  two sources of truth. Now imports REFERENCE_LINE.
- Chat endpoint used the deprecated `call_openrouter` alias and passed
  an explicit `model=` that bypassed the provider chain. Switched to
  `call_llm` with default model selection, then removed the alias.

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

app/routers/api.py

@@ -24,10 +24,11 @@ from app.auth import require_token, maybe_current_user, CurrentUser
 from app.services.i18n import ACTIVE_LANGUAGES
 from app.config import get_settings
 from app.db import get_session, utcnow
+from app.jobs._market_context import REFERENCE_LINE
 from app.services.openrouter import (
     PROMPT_VERSION,
     build_chat_system_prompt,
-    call_openrouter,
+    call_llm,
     month_start,
 )
 from app.templates_env import templates
@@ -710,10 +711,7 @@ class ChatRequest(BaseModel):
     messages: list[ChatMessage]
 
 
-CHAT_REFERENCE_LINE = (
-    "S&P 7,501 (ATH) · VIX 18.0 · US 10y 4.45% · HY OAS 279bps · "
-    "Brent $109/bbl · Gold $4,651/oz · CPI 3.8% YoY"
-)
+
 THESIS_KEYWORDS_FALLBACK = [
     "hormuz", "iran", "opec", "brent", "wti", "crude", "oil",
     "china", "taiwan", "yuan", "fed", "inflation", "cpi", "yield",
@@ -822,7 +820,7 @@ async def chat(
         log_generated_at=log_row.generated_at if log_row else None,
         quotes_by_group=quotes,
         headlines=headlines,
-        reference_line=CHAT_REFERENCE_LINE,
+        reference_line=REFERENCE_LINE,
     )
 
     msgs = [{"role": "system", "content": system_prompt}]
@@ -831,7 +829,7 @@ async def chat(
 
     try:
         async with httpx.AsyncClient(follow_redirects=True) as client:
-            result = await call_openrouter(client, msgs, model=s.OPENROUTER_MODEL)
+            result = await call_llm(client, msgs)
     except Exception as e:
         session.add(AICall(
             model=s.OPENROUTER_MODEL, status="error", error=str(e)[:500],