Sets sqlite as the default DB_CONNECTION, teaches SqliteMigration how
to alter/drop columns via SQLite's table-rebuild pattern (previously
unsupported), and fixes container startup so the sqlite file is owned
by www-data instead of root (was causing "readonly database" errors
on writes). Also adds phpLiteAdmin on port 8081 for browsing the
sqlite database, with a fix for nginx dropping the port from
absolute-URL redirects.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>