HOTFIX web: /status/full 500 (str→tzinfo), /plan/compare 500 (chybějící comparison), canonical PV fn 4.5s→0.4s (force_custom_plan)

1) full_status._iso_utc dostával z JSONB bundle stringy → AttributeError → 500
   celého /status/full; nyní parsuje přes _parse_ts.
2) /plan/compare: NameError — 'comparison = _bundle_from_current(compare_raw)'
   se nikdy nesestavilo (smazaný řádek), endpoint vždy 500.
3) fn_forecast_pv_slots_range_canonical_ab: PG 18 cachuje plány SQL funkcí →
   generický plán 4.5 s / 607k buffers; set plan_cache_mode=force_custom_plan
   → 0.4 s / 34k (změřeno explain analyze na živé DB). Táhne /plan/current,
   /plan/compare i rolling plánovač.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/routers/full_status.py

@@ -40,7 +40,10 @@ HEARTBEAT_STALE_SEC = 300
 EXPECTED_TOMORROW_PRICE_SLOTS = 90
 
 
-def _iso_utc(dt: datetime | None) -> str | None:
+def _iso_utc(dt: datetime | str | None) -> str | None:
+    # JSONB bundle z fn_site_full_status nese timestampy jako stringy — parsovat,
+    # jinak .tzinfo na str = AttributeError → 500 celého /status/full.
+    dt = _parse_ts(dt)
     if dt is None:
         return None
     if dt.tzinfo is None:

backend/app/routers/plan.py

@@ -207,6 +207,7 @@ async def get_plan_compare(
         raise HTTPException(status_code=404, detail="No comparison plan")
 
     active = _bundle_from_current(active_raw)
+    comparison = _bundle_from_current(compare_raw)
     diff, slot_diffs = _build_plan_diff(active, comparison)
     return PlanningCompareResponseModel(
         active=active,

db/routines/R__088_fn_forecast_pv_slots_range_canonical_ab.sql

@@ -28,6 +28,9 @@ returns jsonb
 language sql
 stable
 set work_mem = '64MB'
+-- PG 18 cachuje plány SQL funkcí → generický plán bez znalosti hodnot parametrů
+-- (4.5 s / 607k buffers); s custom planem dle skutečných hodnot 0.4 s / 34k.
+set plan_cache_mode = force_custom_plan
 as $fn$
   with tz as (
     select coalesce(nullif(trim(s.timezone), ''), 'Europe/Prague') as tz_name