Average player age at registration; age-matched round 1 for bracket-only tournaments

Optional age on signup and the desk. Auto-generated brackets pair neighbours by
age with byes spread down the sheet; teams without an age are placed at random,
fully random when no ages exist. Release 0.6.0.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_01MB7nCCAscYsb3zzkT6LHZi

server/views/public.js

@@ -27,6 +27,7 @@ export function registerPage(state, { error = null, values = {} } = {}) {
     <label>Captain's name <input name="captain" required maxlength="60" value="${esc(values.captain ?? '')}"></label>
     <label>Captain's mobile <input name="phone" type="tel" inputmode="tel" maxlength="30" value="${esc(values.phone ?? '')}" placeholder="optional, for organizer contact"></label>
     <label>Number of players <input name="players" type="number" inputmode="numeric" min="${esc(r.teamSize)}" max="20" required value="${esc(values.players ?? r.teamSize)}"></label>
+    <label>Average age of your players <input name="avgAge" type="number" inputmode="numeric" min="5" max="99" value="${esc(values.avgAge ?? '')}" placeholder="e.g. 34"><span class="hint">Optional. We use this to match teams of similar age groups against each other in the first round, for the best play. Teams that skip it are placed at random. Not shown publicly.</span></label>
     <label>Player names <textarea name="playerNames" rows="3" placeholder="one per line (optional)">${esc(values.playerNames ?? '')}</textarea></label>
     <button class="primary" type="submit">Register</button>
     <p class="muted small">After you register you'll get a private team link. Keep this page's QR code handy: once play starts it becomes the live board.</p>