fix: surface empty OHLCV fetch as a warning, not success

Fetching a symbol the provider doesn't cover (e.g. RHM/Rheinmetall — Alpaca
serves US listings only) returned 0 bars but reported "complete · Successfully
ingested 0 records", which the UI showed as green success.

fetch_and_ingest now returns a distinct `no_data` status when the provider
returns nothing AND the ticker has no history (vs. "already up to date" when bars
exist). The fetch endpoint maps it to a `warning` source status, and the fetch
toast renders it as ⚠ with the provider message instead of success.

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

app/services/ingestion_service.py

@@ -30,7 +30,7 @@ class IngestionResult:
     symbol: str
     records_ingested: int
     last_date: date | None
-    status: str  # "complete" | "partial" | "error"
+    status: str  # "complete" | "partial" | "error" | "no_data"
     message: str | None = None
 
 
@@ -143,6 +143,31 @@ async def fetch_and_ingest(
             message=str(exc),
         )
 
+    # Provider returned nothing. With no history at all this almost always means
+    # the provider doesn't cover this symbol (Alpaca = US listings only) — surface
+    # that instead of a misleading "success". With existing bars it just means
+    # there were no new bars in the requested window.
+    if not records:
+        existing = await _get_ohlcv_bar_count(db, ticker.id)
+        if existing == 0:
+            return IngestionResult(
+                symbol=ticker.symbol,
+                records_ingested=0,
+                last_date=None,
+                status="no_data",
+                message=(
+                    "No data returned by the provider — it may not cover this symbol "
+                    "(Alpaca serves US-listed securities only)."
+                ),
+            )
+        return IngestionResult(
+            symbol=ticker.symbol,
+            records_ingested=0,
+            last_date=None,
+            status="complete",
+            message="Already up to date — no new bars.",
+        )
+
     # Sort records by date to ensure ordered ingestion
     records.sort(key=lambda r: r.date)