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/app/schemas.py

@@ -29,6 +29,10 @@ class ServerRegisterRequest(BaseModel):
     mode: Mode
     player_count: int = 0
     max_players: int = 50
+    # See GameServer.game_mode/map_name in app/models.py -- the in-match
+    # GameMode id and map display name, distinct from `mode` (queue mode).
+    game_mode: str = "team_deathmatch"
+    map_name: str = "Sector Alpha"
 
 
 class PlayerStatsResponse(BaseModel):
@@ -39,6 +43,7 @@ class PlayerStatsResponse(BaseModel):
     kills: int
     deaths: int
     hours_played: float
+    ram_kb: int
 
 
 # Reported by the hosting game server (never a client directly -- see