Add webhook-event retention job, schema, and testdb pre-flight hint

square_webhook_events is now CREATE TABLE IF NOT EXISTS, registered as the 24th maintenance job (sweep-square-webhook-events, daily 2:30am) pruning rows older than 90 days, and testdb gives a clear docker compose hint when the admin DB connection fails.

init-scripts/init-script.sql

@@ -2284,6 +2284,18 @@ CREATE TABLE square_deposits (
 
 CREATE INDEX idx_square_deposits_deposited ON square_deposits(deposited_at);
 
+-- =======================================
+-- SQUARE WEBHOOK EVENTS TABLE (Webhook Dedup)
+-- =======================================
+-- Records every Square webhook event_id the handler has accepted. The webhook
+-- handler inserts with ON CONFLICT (event_id) DO NOTHING and treats a 0-row
+-- insert as a duplicate, giving restart-safe, at-most-once delivery with no
+-- eviction limit (unlike the in-memory fast-path cache).
+CREATE TABLE IF NOT EXISTS square_webhook_events (
+    event_id TEXT PRIMARY KEY,
+    received_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
 -- =======================================
 -- CARDDAV / CALDAV TABLES (used by SabreDAV sync in Go backend)
 -- =======================================