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/030_create_sites_table.py

@@ -70,7 +70,11 @@ def upgrade() -> None:
         """)
     )
 
-    # 3. Add nullable site_id FK column to devices table
+    # 3. Grant app_user access
+    conn.execute(sa.text("GRANT SELECT, INSERT, UPDATE, DELETE ON sites TO app_user"))
+    conn.execute(sa.text("GRANT SELECT ON sites TO poller_user"))
+
+    # 4. Add nullable site_id FK column to devices table
     op.add_column(
         "devices",
         sa.Column(