feat: salvage mysql patterns skill (#1733)

- add a maintainer-reviewed MySQL/MariaDB production patterns skill based on PR #1727

- register the skill in database install module and npm publish allowlist

- sync catalog counts to 53 agents, 200 skills, and 69 commands

manifests/install-modules.json

@@ -179,6 +179,7 @@
         "skills/clickhouse-io",
         "skills/database-migrations",
         "skills/jpa-patterns",
+        "skills/mysql-patterns",
         "skills/postgres-patterns"
       ],
       "targets": [