feat: retry failed alert deliveries

lib/db.ts

@@ -90,6 +90,12 @@ CREATE TABLE IF NOT EXISTS error_events (
   id INTEGER PRIMARY KEY, scope TEXT NOT NULL, message TEXT NOT NULL, context_json TEXT,
   created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
 );
+CREATE TABLE IF NOT EXISTS alert_deliveries (
+  id INTEGER PRIMARY KEY, bucket TEXT NOT NULL, title TEXT NOT NULL, message TEXT NOT NULL,
+  status TEXT NOT NULL DEFAULT 'queued', attempts INTEGER NOT NULL DEFAULT 0, last_error TEXT,
+  created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP, started_at TEXT, finished_at TEXT,
+  run_after TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
 CREATE TABLE IF NOT EXISTS source_invites (
   id INTEGER PRIMARY KEY, source_id INTEGER NOT NULL REFERENCES sources(id) ON DELETE CASCADE,
   token_hash TEXT UNIQUE NOT NULL, role TEXT NOT NULL DEFAULT 'viewer', expires_at TEXT NOT NULL,
@@ -172,6 +178,8 @@ const hasFtsMigration = db.prepare("SELECT 1 FROM schema_migrations WHERE versio
 if (!hasFtsMigration) { db.prepare("INSERT INTO posts_fts(rowid,content,tags) SELECT id,content,tags_json FROM posts").run(); db.prepare("INSERT INTO schema_migrations(version) VALUES(39)").run(); }
 db.exec("CREATE INDEX IF NOT EXISTS posts_source_visibility_idx ON posts(source_id,visibility,hidden); CREATE INDEX IF NOT EXISTS posts_author_visibility_idx ON posts(author_id,visibility,hidden);");
 db.prepare("INSERT OR IGNORE INTO schema_migrations(version) VALUES(40)").run();
+db.exec("CREATE INDEX IF NOT EXISTS alert_deliveries_status_idx ON alert_deliveries(status,run_after)");
+db.prepare("INSERT OR IGNORE INTO schema_migrations(version) VALUES(41)").run();
 
 const admin = process.env.ADMIN_USERNAME;
 const adminPassword = process.env.ADMIN_PASSWORD;