4.0.0 - major overhaul

• Refresh pagila-data.sql with more diverse, less repetitive sample data:
  • Grow the customer base from 599 to 999, with signups spread across 2022-2026 instead of a single date
  • Grow rental activity from ~16k to ~51.8k rows, and payments from ~16k to ~51k rows, spanning January 2022 through July 2026 instead of a few months in 2022
  • Randomize last_update/create_date timestamps across all tables instead of reusing one fixed value per table
• Add 48 new monthly partitions to the payment table in pagila-schema.sql (Aug 2022 - Jul 2026) to support the extended date range
• Add scripts/add_monthly_data.sh to keep a running pagila instance current: creates the next payment partition and populates a month of new rental/payment activity, meant to be scheduled monthly
• Rework the actor_info view to return a JSONB column (film titles grouped by category) instead of a concatenated text string, so it's a domain-relevant example for practicing JSONB operators (fixes #21)
• Change language.name from character(20) to text, and strip the trailing blank-padding it left in the shipped data, matching the text-everywhere convention used by every other column (fixes #33)
• Document PostgreSQL 17's SQL/JSON query functions (JSON_EXISTS(), JSON_VALUE(), JSON_QUERY()), JSON_TABLE(), and the constructor functions (JSON(), JSON_SCALAR(), JSON_SERIALIZE()) in the README, with example queries verified against actor_info
• Raise the minimum supported PostgreSQL version to 18
• Bump docker-compose.yml to the postgres:18 image, and move the pgdata volume mount from /var/lib/postgresql/data to /var/lib/postgresql — the 18+ images refuse to start with a volume mounted at the old path (see docker-library/postgres#1259); verified with a full docker compose up
• Set POSTGRES_DB: pagila in docker-compose.yml (and fix restore-pagila-data-jsonb.sh to restore into it) so docker-compose up actually loads data into a pagila database, matching the README's own \c pagila instructions instead of silently loading everything into the default postgres database
• Add a uuid column (DEFAULT uuidv7(), unique-indexed) to customer, rental, and payment, demonstrating PostgreSQL 18's new UUID functions
• Regenerate pagila-insert-data.sql from the same data as pagila-data.sql — it had drifted badly out of sync (e.g. every film's release_year was hardcoded to 2006 regardless of the real value), fixes #39
• Fix 400 of the 999 customers added in the 4.0.0 data refresh all being named "ELIZABETH HALL" — an uncorrelated scalar subquery in the name-generation script was evaluated once instead of per-row (the same bug class as the earlier create_date fix); regenerated with proper per-row random names
• Add a Dockerfile (building pg_partman 5.5.0 from source on postgres:18) and hand the payment table's future partitions over to it instead of creating them by hand, while leaving the existing Jan 2022 - Jul 2026 partitions untouched; maintenance runs via scripts/run_partman_maintenance.sh on cron (partman.run_maintenance_proc(0, true, true)) rather than pg_partman's own background worker, and scripts/add_monthly_data.sh calls the same procedure as a safety net