feat(triggers): add schedule trigger kind + internal scheduler

Fourth trigger kind alongside registry/git/manual. Recurring time-interval
fires driven by a new internal/scheduler tick loop (default 30s, clamped
to 5m). Goes through the same webhook.Handler.FanOutForTrigger seam as
inbound HTTP webhooks, so per-binding concurrency, outcome accounting,
and config-merge semantics are identical.

Schema: triggers.last_fired_at TEXT column (additive ALTER for existing
DBs). Scheduler persists last_fired_at BEFORE dispatch so a panicking
Match cannot wedge a tight loop; failed deploys wait one full interval
before retry — correct trade-off for a periodic refresh trigger.

Frontend: TriggerKindForm + /triggers/new + /triggers/[id] gain the
schedule kind (4-col card grid, preset chips Hourly/Daily/Weekly,
custom interval input matched to Go time.ParseDuration syntax, optional
pinned reference). /triggers/[id] surfaces "last fired" on schedule rows.
EN+RU i18n in parity.

Review fixes from go-reviewer / security-reviewer / typescript-reviewer:
- Scheduler Start/Stop wrapped in sync.Once (no goroutine leak / double-
  cancel panic on shutdown re-entry).
- shouldFire rejects sub-MinInterval as defense-in-depth against
  hand-inserted rows that bypassed Validate.
- fire() asserts trigger Kind=="schedule" before dispatching.
- Aligned isValidInterval regex across all three frontend sites; reject
  the unsupported "d" unit (Go time.ParseDuration doesn't accept it).
- formatLastFired falls back to lastFiredNever on malformed timestamps
  rather than leaking raw bytes into the UI.
- main.go scheduler closure logs per-fire deployed/errored counts.

internal/store/triggers.go

@@ -10,14 +10,14 @@ import (
 
 const triggerColumns = `id, kind, name, config,
 	webhook_secret, webhook_signing_secret, webhook_require_signature,
-	created_at, updated_at`
+	last_fired_at, created_at, updated_at`
 
 func scanTrigger(s rowScanner) (Trigger, error) {
 	var t Trigger
 	var requireSig int
 	if err := s.Scan(&t.ID, &t.Kind, &t.Name, &t.Config,
 		&t.WebhookSecret, &t.WebhookSigningSecret, &requireSig,
-		&t.CreatedAt, &t.UpdatedAt); err != nil {
+		&t.LastFiredAt, &t.CreatedAt, &t.UpdatedAt); err != nil {
 		return Trigger{}, err
 	}
 	t.WebhookRequireSignature = requireSig != 0
@@ -38,10 +38,10 @@ func (s *Store) CreateTrigger(t Trigger) (Trigger, error) {
 	t.UpdatedAt = t.CreatedAt
 	_, err := s.db.Exec(
 		`INSERT INTO triggers (`+triggerColumns+`)
-		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
 		t.ID, t.Kind, t.Name, t.Config,
 		t.WebhookSecret, t.WebhookSigningSecret, BoolToInt(t.WebhookRequireSignature),
-		t.CreatedAt, t.UpdatedAt,
+		t.LastFiredAt, t.CreatedAt, t.UpdatedAt,
 	)
 	if err != nil {
 		return Trigger{}, fmt.Errorf("insert trigger: %w", translateSQLError(err))
@@ -139,7 +139,7 @@ func (s *Store) ListTriggersWithBindingCount(kind string) ([]TriggerWithBindingC
 	const base = `
 		SELECT t.id, t.kind, t.name, t.config,
 			t.webhook_secret, t.webhook_signing_secret, t.webhook_require_signature,
-			t.created_at, t.updated_at,
+			t.last_fired_at, t.created_at, t.updated_at,
 			COALESCE(b.cnt, 0)
 		FROM triggers t
 		LEFT JOIN (
@@ -166,7 +166,7 @@ func (s *Store) ListTriggersWithBindingCount(kind string) ([]TriggerWithBindingC
 		var count int
 		if err := rows.Scan(&t.ID, &t.Kind, &t.Name, &t.Config,
 			&t.WebhookSecret, &t.WebhookSigningSecret, &requireSig,
-			&t.CreatedAt, &t.UpdatedAt, &count); err != nil {
+			&t.LastFiredAt, &t.CreatedAt, &t.UpdatedAt, &count); err != nil {
 			return nil, fmt.Errorf("scan trigger+count: %w", err)
 		}
 		t.WebhookRequireSignature = requireSig != 0
@@ -236,10 +236,10 @@ func (s *Store) CreateTriggerWithBindingTx(t Trigger, b WorkloadTriggerBinding)
 	t.UpdatedAt = t.CreatedAt
 	if _, err := tx.Exec(
 		`INSERT INTO triggers (`+triggerColumns+`)
-		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
 		t.ID, t.Kind, t.Name, t.Config,
 		t.WebhookSecret, t.WebhookSigningSecret, BoolToInt(t.WebhookRequireSignature),
-		t.CreatedAt, t.UpdatedAt,
+		t.LastFiredAt, t.CreatedAt, t.UpdatedAt,
 	); err != nil {
 		return Trigger{}, WorkloadTriggerBinding{}, fmt.Errorf("insert trigger: %w", translateSQLError(err))
 	}
@@ -301,3 +301,24 @@ func (s *Store) EnsureTriggerWebhookSecret(id string) (string, error) {
 	}
 	return secret, nil
 }
+
+// SetTriggerLastFired records the wall-clock the scheduler last
+// dispatched this trigger. Callers pass time.Now().UTC().Format(time.RFC3339)
+// so the value is stable across timezones. Updating last_fired_at does
+// not bump updated_at — last_fired_at is operational state, while
+// updated_at tracks user-visible config edits.
+func (s *Store) SetTriggerLastFired(id, ts string) error {
+	result, err := s.db.Exec(
+		`UPDATE triggers SET last_fired_at = ? WHERE id = ?`,
+		ts, id,
+	)
+	if err != nil {
+		return fmt.Errorf("update trigger last_fired_at: %w", err)
+	}
+	n, _ := result.RowsAffected()
+	if n == 0 {
+		return fmt.Errorf("trigger %s: %w", id, ErrNotFound)
+	}
+	return nil
+}
+