PgPartman Support

[yknx4]

closes #9

This pull request introduces comprehensive support for multi-schema migrations and the pg_partman extension in the Heroku-to-PlanetScale migration workflow. It adds fine-grained schema inclusion/exclusion controls, ensures correct handling of generated columns and partitioned tables across schemas, and improves documentation and dashboard guidance for users migrating complex databases.

Multi-schema and pg_partman support:

• Added MIGRATION_SCHEMAS and MIGRATION_EXCLUDE_SCHEMAS environment variables to allow users to specify which schemas to include or exclude during migration, defaulting to public and excluding common extension/internal schemas. The migrator now processes schemas accordingly throughout the migration process, including schema copy, Bucardo configuration, and generated column handling. (README.md, AGENTS.md, scripts/mk-bucardo-repl.sh) [1] [2] [3] [4] [5] [6]
• Added explicit documentation and migration steps for supporting pg_partman, including instructions for pausing jobs, installing the extension, and manually applying generated SQL to recreate partition sets on PlanetScale. The dashboard now surfaces preflight information and SQL for pg_partman-managed tables. (README.md, AGENTS.md, status-server/dashboard.html) [1] [2] [3] [4]

Generated columns and schema-aware queries:

• Updated all queries and scripts to handle schemas explicitly, ensuring generated columns and tables without primary keys are detected and processed across all included schemas, not just public. (AGENTS.md, scripts/mk-bucardo-repl.sh) [1] [2] [3] [4] [5] [6] [7]
• Adjusted manual and automated steps for handling generated columns to use <schema>.<table> notation and to operate across all included schemas. (AGENTS.md, scripts/mk-bucardo-repl.sh) [1] [2] [3]

Operational improvements and configuration:

• Added Bucardo runtime TCP keepalive settings to improve reliability of replication connections, especially for long-running migrations. (entrypoint.sh, scripts/mk-bucardo-repl.sh) [1] [2]
• Enhanced migration and cutover steps to operate across all configured schemas, including correct SQL for revoking privileges and dropping triggers in all relevant schemas. (README.md, AGENTS.md) [1] [2]

Documentation and dashboard enhancements:

• Updated documentation to reflect new multi-schema and pg_partman workflows, including environment variable usage, troubleshooting, and schema-aware examples. (README.md, AGENTS.md) [1] [2] [3]
• Improved dashboard preflight checks to display pg_partman status, parent tables, and generated SQL for user action. (status-server/dashboard.html) [1] [2] [3]