feat(webhook): inbound delivery audit log

Persists every inbound webhook hit (project + site) so users can debug
"why didn't my deploy fire?" without grepping daemon logs. Surfaces a
14-day rolling history under the WebhookPanel on each project + site
detail page; refreshes every 30s while open. Daily cron prunes records
older than 14 days alongside the existing event log prune.

Schema:
- webhook_deliveries(id, target_type, target_id, target_name, received_at,
  source_ip, signature_state, status_code, outcome, detail, body_size)
- indexes on (target_type,target_id,received_at) and (received_at)

Backend:
- store: WebhookDelivery model + Insert/List/Prune helpers
- webhook/handler: deferred recordDelivery() captures the final outcome
  on every return path including HMAC rejects, image mismatch, no-stage,
  auto_deploy=false, and successful deploys; signatureStateFor()
  classifies "unconfigured" vs "missing" vs "invalid" vs "valid"
- api: GET /api/{projects,sites}/{id}/webhook/deliveries with
  parseLimit() helper (default 50, max 200)
- main: daily prune cron retains the last 14 days

Frontend:
- WebhookDeliveryLog.svelte: panel with refresh button, status code +
  outcome + signature badges, relative time tooltip-on-hover for
  absolute time, source IP column
- Mounted below WebhookPanel on project + site detail pages
- en/ru i18n strings for outcome/signature enums and column labels

internal/store/store.go

@@ -159,6 +159,24 @@ func (s *Store) runMigrations() error {
 		`ALTER TABLE projects ADD COLUMN webhook_require_signature INTEGER NOT NULL DEFAULT 0`,
 		`ALTER TABLE static_sites ADD COLUMN webhook_signing_secret TEXT NOT NULL DEFAULT ''`,
 		`ALTER TABLE static_sites ADD COLUMN webhook_require_signature INTEGER NOT NULL DEFAULT 0`,
+		// Webhook delivery audit log (2026-05-07). Persists every inbound
+		// webhook request (project or site) with its outcome so users can
+		// debug "why didn't my deploy fire?" without grepping daemon logs.
+		`CREATE TABLE IF NOT EXISTS webhook_deliveries (
+			id              INTEGER PRIMARY KEY AUTOINCREMENT,
+			target_type     TEXT NOT NULL,
+			target_id       TEXT NOT NULL DEFAULT '',
+			target_name     TEXT NOT NULL DEFAULT '',
+			received_at     TEXT NOT NULL DEFAULT (datetime('now')),
+			source_ip       TEXT NOT NULL DEFAULT '',
+			signature_state TEXT NOT NULL DEFAULT '',
+			status_code     INTEGER NOT NULL DEFAULT 0,
+			outcome         TEXT NOT NULL DEFAULT '',
+			detail          TEXT NOT NULL DEFAULT '',
+			body_size       INTEGER NOT NULL DEFAULT 0
+		)`,
+		`CREATE INDEX IF NOT EXISTS idx_webhook_deliveries_target ON webhook_deliveries(target_type, target_id, received_at)`,
+		`CREATE INDEX IF NOT EXISTS idx_webhook_deliveries_received_at ON webhook_deliveries(received_at)`,
 	}
 
 	// Additive stack tables (2026-04-16). Created here rather than in the