Read the recorded snooze outcomes back out of the nudges table (#364)

The gate honours State.SnoozeUntil but nothing ever filled it. New
store.SnoozedUntil returns, per rule, when the newest snooze runs out.
Reviewer: the fixed 2h SnoozeDuration and its reasoning in nudges.go —
nothing upstream can supply a per-nudge length, so no new column.
Expired snoozes are dropped in SQL, so silence can never be permanent.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CGeSZxh1DCtRxmFVSYVGvJ

internal/store/migrations.go

@@ -70,6 +70,8 @@ ALTER TABLE reminders ADD COLUMN next_fire_ts INTEGER;`, // #2
 		CHECK (resolution_state IN ('none','pending','resolved','ambiguous','not_found'));
 	CREATE INDEX IF NOT EXISTS idx_facts_entity_id ON facts (entity_id) WHERE entity_id IS NOT NULL;
 	CREATE INDEX IF NOT EXISTS idx_facts_resolution_pending ON facts (resolution_state) WHERE resolution_state = 'pending';`, // #7 — entity-aware memory (Vikunja #279): facts about a subject get resolved to a Nexus entity_id async
+
+	`CREATE INDEX IF NOT EXISTS idx_nudges_snoozed ON nudges (outcome_ts) WHERE outcome = 'snoozed';`, // #8 — SnoozedUntil runs every tick; keep it off a full scan (Vikunja #364)
 }
 
 // migrate applies every migration with a number greater than the DB's current