Add game mode categories, character creation, on-foot ship/hub mode, RAM currency, and in-ship navigation

Bundles several sessions' worth of previously uncommitted work: map
categories with Domination/Conquest/King of the Hill mode stubs and a
server-list mode filter; a procedurally-drawn character-creation screen
replacing the old callsign-only PROFILE overlay; the on-foot groundwork
(walkable station hub, ship interior, character controller) plus the RAM
currency backend; and today's addition, an in-ship Helldivers-2-style
navigation table that QUICK PLAY's queue/connect flow and the Belters/
Military hub travel now live behind, with hub-and-ship return paths and a
context-aware pause menu usable both in-match and inside the ship.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

matchmaking-api/README.md

@@ -106,6 +106,28 @@ add them to a database that already has a `players` table from before this
 change. Run `docker compose down -v` once to pick them up on an existing local
 dev database.
 
+## RAM (in-game currency)
+
+See `overview/onfoot.md` for the full design — this is just the backend
+piece. `Player.ram_kb` is a single `BigInteger` balance, always stored and
+transmitted as kilobytes (the smallest denomination); the Godot client
+(`spacewar/autoload/currency.gd`) formats it up into KB/MB/GB/TB for
+display, 1000 per step. 100% separate from real-money monetization
+(`overview/money.md`) — this is purely an in-game economy.
+
+`POST /matches/report` now also credits RAM to every reported player:
+`ram_payout_participation_kb` just for being in the match, plus
+`ram_payout_per_kill_kb` per kill, plus `ram_payout_win_bonus_kb` if they
+won (all three tunable in `app/config.py`, currently 50/15/200 — placeholder
+numbers, not balanced against anything). `GET /stats/{callsign}` returns the
+running total as `ram_kb`.
+
+There is no spend endpoint yet — nothing in the game can spend RAM until the
+ship interior/hubs from `overview/onfoot.md` exist. `Player.ram_kb` is a new
+column on an existing table, same no-migrations caveat as above — covered by
+the same `docker compose down -v` if you're picking this up on an existing
+local dev database.
+
 ## Client integration
 
 The Godot client is wired up (`spacewar/autoload/matchmaking_client.gd`):