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/schemas/target.py

@@ -9,6 +9,7 @@ class TargetBase(BaseModel):
     dbname: str
     username: str
     sslmode: str = "prefer"
+    use_pg_stat_statements: bool = True
     tags: dict = Field(default_factory=dict)
 
 
@@ -33,6 +34,7 @@ class TargetUpdate(BaseModel):
     username: str | None = None
     password: str | None = None
     sslmode: str | None = None
+    use_pg_stat_statements: bool | None = None
     tags: dict | None = None