feat: chip-based player entry with session stat strip

[kangooroux]

Summary

Reworks the player-entry UX from textareas to interactive chip inputs, and adds a session stat strip to the results view. Ported from the Claude Design "Session Summary" concept, adapted to the app's conventions (plain CSS, CSP-safe, a11y preserved). No backend changes — chips serialize into the existing players + custom_pod[] fields on submit.

Changes

• Chip inputs replace the player/custom-pod textareas. Add via Enter, remove via the chip's × button, Backspace clears the last chip.
• Custom tables: each is a card with a live n/4 count, a max of 4 players, and a guard against empties — "+ Add custom table" goes inert (dimmed, not-allowed) while any table is still empty.
• Bulk entry preserved: pasting a list (newline/comma-separated) splits into multiple chips, and duplicates are de-duped case-insensitively.
• Results stat strip (players / pods counts) + a dated subtitle in the results header; Print pushed to the opposite edge.
• All new styling in app.css (plain CSS, rem, existing tokens); all interactivity in app.js (no inline styles/handlers → CSP-safe).

Files

• templates/group/index.html.twig
• public/css/app.css
• public/js/app.js

Verification done locally

• node --check public/js/app.js passes.
• End-to-end round-trip: submit (serialized players + custom_pod[]) → results render with correct player/pod counts → remaining players re-seed as chips from session rawInput.

To verify in review

• Browser: add/remove chips, paste a list, per-table n/4 count, add-table guard toggling inert.
• Light + dark themes.
• Keyboard + screen-reader flow (sr-live announcements, aria-labels).
• Multi-round: Randomize → Next Round → Reset.
• Print view unaffected.