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/app/models/models.py

@@ -27,6 +27,7 @@ class Target(Base):
     username: Mapped[str] = mapped_column(String(120), nullable=False)
     encrypted_password: Mapped[str] = mapped_column(Text, nullable=False)
     sslmode: Mapped[str] = mapped_column(String(20), nullable=False, default="prefer")
+    use_pg_stat_statements: Mapped[bool] = mapped_column(Boolean, nullable=False, default=True)
     tags: Mapped[dict] = mapped_column(JSON, nullable=False, default=dict)
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now(), nullable=False)