fix(database_query): keep psql's command tags out of the returned rows

With `-tA` psql drops headers and the row-count footer but still prints
the command tag of every write statement. A guarded
`UPDATE … RETURNING` that matched nothing therefore came back as
`rows: [['UPDATE 0']]`, and web-app-peertube's oidc/enable.yml, which
judges its change by the row count, reported `changed` and restarted
PeerTube on every deploy after the first.

The PostgreSQL rows flags are now `-qtA`. Probed against a running
postgres container:

    -tA  -> CREATE TABLE / INSERT 0 1 / UPDATE 0 / 3 / UPDATE 1
    -qtA -> 3

SELECT output and the MariaDB path (`--batch --skip-column-names`, no
status line) are unchanged.

Fixes #1164

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

library/database_query.py

@@ -109,7 +109,7 @@ _ENGINES: dict[str, dict[str, object]] = {
         "user_flag": "-U",
         "db_flag": "-d",
         "shared_flags": ["-v", "ON_ERROR_STOP=1"],
-        "rows_flags": ["-tA"],
+        "rows_flags": ["-qtA"],
         "row_separator": "|",
         "password_env": "PGPASSWORD",
         "string_quote": "'",

tests/unit/python/library/test_database_query.py

@@ -93,13 +93,13 @@ class BuildCmdPostgresTests(unittest.TestCase):
         self.assertIn("ON_ERROR_STOP=1", cmd)
         self.assertNotIn("s3cret", cmd)
 
-    def test_postgres_expect_rows_adds_tuples_only_flag(self):
+    def test_postgres_expect_rows_adds_quiet_tuples_only_flag(self):
         cmd, _ = _DB_MOD._build_cmd(_BASE_CONFIG, expect_rows=True)
-        self.assertIn("-tA", cmd)
+        self.assertIn("-qtA", cmd)
 
     def test_postgres_no_rows_omits_tuples_only_flag(self):
         cmd, _ = _DB_MOD._build_cmd(_BASE_CONFIG, expect_rows=False)
-        self.assertNotIn("-tA", cmd)
+        self.assertNotIn("-qtA", cmd)
 
 
 class BuildCmdMariadbTests(unittest.TestCase):