PgvectorDocumentStore: DB not initialized in delete_table method

[antrix]

Describe the bug
The delete_table() and delete_table_async() methods do not call _ensure_db_setup() first. Thus, if delete_table() is the first call on the document store, it will fail.

To Reproduce

1. Create a PgvectorDocumentStore instance.
2. Call delete_table() on the instance.

app-sg-1 |  File "/app/core/admin.py", line 90, in save_model
app-sg-1 |    store.delete_table()
app-sg-1 |    ~~~~~~~~~~~~~~~~~~^^
app-sg-1 |  File "/py/lib/python3.13/site-packages/haystack_integrations/document_stores/pgvector/document_store.py", line 500, in delete_table
app-sg-1 |    self._execute_sql(
app-sg-1 |    ~~~~~~~~~~~~~~~~~^
app-sg-1 |        delete_sql,
app-sg-1 |        ^^^^^^^^^^^
app-sg-1 |        error_msg=f"Could not delete table {self.schema_name}.{self.table_name} in PgvectorDocumentStore",
app-sg-1 |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
app-sg-1 |    )
app-sg-1 |    ^
app-sg-1 |  File "/py/lib/python3.13/site-packages/haystack_integrations/document_stores/pgvector/document_store.py", line 270, in _execute_sql
app-sg-1 |    raise ValueError(message)
app-sg-1 |ValueError: The cursor or the connection is not initialized. Make sure to call _ensure_db_setup() before calling this method.

Describe your environment (please complete the following information):

• OS: MacOS, Linux
• Haystack version: haystack-ai==2.11.2
• Integration version: pgvector-haystack==3.2.0