fix bulk fundamentals: rate limits masked by partial FMP success

Root cause of "price plan needed in bulk but fine on manual reload": on free
tiers FMP returns only market cap (others 402) and the chain merged that as a
partial success — so when the Finnhub/Alpha Vantage fallbacks were rate-limited
during a bulk run, the chain silently returned market-cap-only and the
collector's backoff never engaged. Manual single fetches worked because the
fallbacks weren't throttled at that moment.

Fixes:
- Chain distinguishes RateLimitError from other failures: if a fallback is
  rate-limited and fields are still missing, raise RateLimitError (unless
  allow_partial=True) so the collector backs off and retries.
- Bulk job paces requests (fundamental_request_spacing_seconds, default 3s) to
  stay under Finnhub's ~60/min, and on retry-exhaustion stores partial data and
  continues instead of aborting the whole run.
- Manual fetch passes allow_partial=True so a lone 429 doesn't fail the refresh.

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

app/routers/ingestion.py

@@ -159,7 +159,11 @@ async def fetch_symbol(
         if settings.fmp_api_key or settings.finnhub_api_key or settings.alpha_vantage_api_key:
             try:
                 fundamentals_provider = build_fundamental_provider_chain()
-                fdata = await fundamentals_provider.fetch_fundamentals(symbol_upper)
+                # Manual single fetch: take whatever we can get (a lone 429 on a
+                # fallback shouldn't fail the whole refresh).
+                fdata = await fundamentals_provider.fetch_fundamentals(
+                    symbol_upper, allow_partial=True
+                )
                 await fundamental_service.store_fundamental(
                     db,
                     symbol=symbol_upper,