fix(db): add missing GRANT statements to v9.7 migrations

Migrations 030 (sites), 032 (device_interfaces), 033 (wireless_links),
and 034 (sectors) were missing GRANT statements for app_user and
poller_user. Without these, fresh deploys crash on site/sector CRUD
with permission denied errors. Also added poller_user SELECT grants
to migration 035 (site_alert_rules/events).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/alembic/versions/035_site_alert_rules_and_events.py

@@ -184,6 +184,7 @@ def upgrade() -> None:
         """)
     )
     conn.execute(sa.text("GRANT SELECT, INSERT, UPDATE, DELETE ON site_alert_rules TO app_user"))
+    conn.execute(sa.text("GRANT SELECT ON site_alert_rules TO poller_user"))
 
     # site_alert_events RLS
     conn.execute(sa.text("ALTER TABLE site_alert_events ENABLE ROW LEVEL SECURITY"))
@@ -202,6 +203,7 @@ def upgrade() -> None:
         """)
     )
     conn.execute(sa.text("GRANT SELECT, INSERT, UPDATE, DELETE ON site_alert_events TO app_user"))
+    conn.execute(sa.text("GRANT SELECT ON site_alert_events TO poller_user"))
 
 
 def downgrade() -> None: