Import Melee matches exports, add tests and local podman stack

- Parse Melee matches exports (one round per file, byes, null GameWins);
  one import form detects matches vs standings exports. Re-importing a
  round replaces just that round and keeps entered decks.
- Per-player deck entry for sessions scored from matches.
- node:test suite with anonymised fixtures; lockfile.
- scripts/local.sh runs the compose stack under podman with its own
  .env.local, project name and volume.
- README and CLAUDE.md docs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -1,2 +1,6 @@
 node_modules
 .env
+# Melee exports contain personal details (Discord names, DCI numbers)
+matches-export-*.json
+Standings-*.json
+.env.local