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

docs/ORGANIZER-GUIDE.md

@@ -12,14 +12,14 @@ Everything an organizer does happens at `/admin` on a phone or laptop. Sign in w
 
 ## Check-in
 
-Teams scan the code and fill in team name, captain, mobile, number of players, optional player names. They get a private team link on the confirmation screen with a "Text it to myself" button. The team link shows their schedule, record, and alerts all day.
+Teams scan the code and fill in team name, captain, mobile, number of players, an optional average player age, and optional player names. They get a private team link on the confirmation screen with a "Text it to myself" button. The team link shows their schedule, record, and alerts all day.
 
 From the desk you can rename a team, fix the captain or player count, remove a team, add a walk-up team, and set seeds (1 = strongest). Seeds decide pool placement (snake order) and bracket placement. If you don't seed, registration order is used.
 
 ## Starting play
 
 1. **Close registration.** The public page switches to the roster and "schedule coming."
-2. **Generate pools** (pick the pool size) or, for bracket-only, generate the bracket. You can clear and regenerate freely until the first score is entered. A late team? Clear generated play, add the team, regenerate.
+2. **Generate pools** (pick the pool size) or, for bracket-only, generate the bracket. For bracket-only days, "Match round 1 by similar age" (on by default) sorts teams by the average age they gave at registration and pairs neighbours, drops teams without an age in at random, and spreads byes so second-round opponents are close in age too; untick it to use seed order. You can clear and regenerate freely until the first score is entered. A late team? Clear generated play, add the team, regenerate.
    To decide the first-round matchups yourself, open **Build the bracket by hand**: one row per round-1 match with a team picker on each side, pre-filled with standard seeding. Leave a side as "bye" to give the other team a walkover. Every team must appear exactly once; winners of matches 1 and 2 meet next, 3 and 4 meet, and so on down the sheet.
 3. **Go live.** The engine immediately assigns the first matches to the courts. Teams whose match is next see "on deck for Court 2, ~15 min" on their team page and the public board.