fix(journal): wire weather refresh on config save; drop orphaned cache rows

Two related gaps in the journal weather panel:

1. Saving locations via PUT /journal/config didn't trigger a weather
   fetch, so newly-entered sites had no cache row (or a stale one) until
   the user manually clicked the panel's refresh button. The panel
   rendered "two sites with empty values" against pre-existing cache
   rows that no longer matched what the user had configured.

2. get_cached_weather_rows returned every WeatherCache row for the user
   regardless of whether the location was still in journal_config.
   Briefing-era rows survived migration 0040 (which only deleted the
   briefing_config setting, not the cache table) and showed up as
   ghost tabs in the UI.

Changes:
- get_cached_weather_rows accepts an optional valid_keys filter; rows
  whose location_key is not in the set are excluded.
- routes/journal.py:
  - put_config kicks off a background refresh_location_cache for any
    saved location with valid lat/lon.
  - GET /weather and POST /weather/refresh both pass valid_keys derived
    from the current config so orphaned rows don't surface.
- services/journal_prep.py filters the weather section to currently-
  configured locations as well; uses a lazy import of get_journal_config
  to avoid a cycle (journal_scheduler imports journal_prep).

153 tests pass.

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

src/fabledassistant/services/journal_prep.py

@@ -178,7 +178,15 @@ async def gather_daily_sections(
         sections["events"] = []
 
     try:
-        weather_rows = await get_cached_weather_rows(user_id)
+        # Lazy import: journal_scheduler imports this module for prep generation,
+        # so a top-level import would cycle.
+        from fabledassistant.services.journal_scheduler import get_journal_config
+        cfg = await get_journal_config(user_id)
+        valid_weather_keys = {
+            key for key, loc in (cfg.get("locations") or {}).items()
+            if isinstance(loc, dict) and loc.get("lat") is not None and loc.get("lon") is not None
+        }
+        weather_rows = await get_cached_weather_rows(user_id, valid_weather_keys)
         sections["weather"] = [w.to_dict() for w in weather_rows]
     except Exception:
         logger.exception("daily_prep weather section failed for user %d", user_id)