Add support for pg_stat_statements configuration in Targets

This commit introduces a `use_pg_stat_statements` flag for targets, allowing users to enable or disable the use of `pg_stat_statements` for query insights. It includes database schema changes, backend logic, and UI updates to manage this setting in both creation and editing workflows.

backend/alembic/versions/0003_target_pg_stat_statements_flag.py

@@ -0,0 +1,26 @@
+"""add target pg_stat_statements flag
+
+Revision ID: 0003_target_pg_stat_statements_flag
+Revises: 0002_alert_definitions
+Create Date: 2026-02-12
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "0003_target_pg_stat_statements_flag"
+down_revision = "0002_alert_definitions"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column(
+        "targets",
+        sa.Column("use_pg_stat_statements", sa.Boolean(), nullable=False, server_default=sa.text("true")),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("targets", "use_pg_stat_statements")