Add created_at to pairs for pair growth stats

Migration 000016. Existing 825 rows keep created_at=0 (we can't
backfill accurately); new /bridge pairs get a real unix timestamp.

SQLite uses INSERT … ON CONFLICT … DO UPDATE SET prefix=0 (previously
INSERT OR REPLACE, which would have wiped created_at on conflict).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

migrations/postgres/000016_pairs_created_at.down.sql

@@ -0,0 +1 @@
+ALTER TABLE pairs DROP COLUMN created_at;

migrations/postgres/000016_pairs_created_at.up.sql

@@ -0,0 +1 @@
+ALTER TABLE pairs ADD COLUMN created_at BIGINT NOT NULL DEFAULT 0;

migrations/sqlite/000016_pairs_created_at.down.sql

@@ -0,0 +1 @@
+ALTER TABLE pairs DROP COLUMN created_at;

migrations/sqlite/000016_pairs_created_at.up.sql

@@ -0,0 +1 @@
+ALTER TABLE pairs ADD COLUMN created_at INTEGER NOT NULL DEFAULT 0;

postgres.go

@@ -64,8 +64,8 @@ func (r *pgRepo) Register(key, platform string, chatID int64) (bool, string, err
 	}
 
 	_, err = r.db.Exec(
-		"INSERT INTO pairs (tg_chat_id, max_chat_id, prefix) VALUES ($1, $2, 0) ON CONFLICT (tg_chat_id, max_chat_id) DO NOTHING",
+		"INSERT INTO pairs (tg_chat_id, max_chat_id, prefix, created_at) VALUES ($1, $2, 0, $3) ON CONFLICT (tg_chat_id, max_chat_id) DO NOTHING",
-		tgID, maxID)
+		tgID, maxID, time.Now().Unix())
 	return true, "", err
 }
 

sqlite.go

@@ -60,7 +60,10 @@ func (r *sqliteRepo) Register(key, platform string, chatID int64) (bool, string,
 		tgID, maxID = peerChatID, chatID
 	}
 
-	_, err = r.db.Exec("INSERT OR REPLACE INTO pairs (tg_chat_id, max_chat_id, prefix) VALUES (?, ?, 0)", tgID, maxID)
+	_, err = r.db.Exec(
+		`INSERT INTO pairs (tg_chat_id, max_chat_id, prefix, created_at) VALUES (?, ?, 0, ?)
+		 ON CONFLICT(tg_chat_id, max_chat_id) DO UPDATE SET prefix = 0`,
+		tgID, maxID, time.Now().Unix())
 	return true, "", err
 }