One deck form per session; rename leagues; e2e test script

- A player's deck for a night is edited in a single form and written to
  their match rows and their standings row, so the two can't disagree.
  Matches, standings and hand imports all fill blank decks from the decks
  already entered, whatever order the files are imported in. The imported
  standings table shows decks read-only.
- Admins can rename a league.
- test/e2e.sh runs end-to-end checks against the local podman stack
  (fixtures by default, or real exports: test/e2e.sh sampledata).

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

README.md

@@ -15,6 +15,7 @@ Sub-path hosting: set `BASE_PATH=/mtg` and proxy with Caddy `handle_path /mtg/*`
 npm install
 npm test          # parser + standings tests
 npm run check     # type-check
+scripts/local.sh up && test/e2e.sh [sampledata]   # end-to-end checks against the local podman stack
 DATABASE_URL=postgres://... SECRET_KEY=... ADMIN_PASSWORD=... npm run dev
 ```
 Whole stack locally with podman (own `.env.local` with generated secrets, own project/volume, port 8889):