feat(admin-console): Stage 4 — games & runtimes domain

Add the games, runtime, and engine-version pages over the existing lobby,
runtime, and engine-version services (no new business logic).

- GET/POST /_gm/games                         list + create public game
- GET      /_gm/games/{id}                    detail incl. runtime snapshot
- POST     /_gm/games/{id}/force-start|stop    game state actions
- POST     /_gm/games/{id}/ban-member          ban a member (uuid + reason)
- POST     /_gm/games/{id}/runtime/restart|patch|force-next-turn
- GET/POST /_gm/engine-versions               registry + register
- POST     /_gm/engine-versions/{ver}/disable disable a version

Console depends on GameAdmin / RuntimeAdmin / EngineVersionAdmin interfaces
(satisfied by the concrete services) so the pages render in tests without a
database. Collection-mutating POSTs are mounted on the collection path to avoid
a static-vs-param route conflict in gin. Writes flow through the CSRF guard and
redirect back; the create form parses datetime-local as UTC.

Tests: list/detail (with and without a runtime), create (visibility/owner/time
assertions), force-start (+ bad-CSRF), ban-member (+ bad uuid), runtime patch
(+ missing version), engine-version list/register/disable, and unavailable.

Docs: backend/docs/admin-console.md page inventory extended.

backend/internal/adminconsole/templates/pages/game_detail.gohtml

@@ -0,0 +1,65 @@
+{{define "content" -}}
+{{$csrf := .CSRFToken}}
+{{with .Data}}
+<p><a href="/_gm/games">&laquo; all games</a></p>
+<h1>{{if .GameName}}{{.GameName}}{{else}}(unnamed){{end}}</h1>
+
+<section class="panel">
+<h2>Game</h2>
+<ul class="kv">
+<li>Game ID: <code>{{.GameID}}</code></li>
+<li>Visibility: {{.Visibility}}</li>
+<li>Status: {{.Status}}</li>
+<li>Owner: {{.Owner}}</li>
+<li>Players: {{.MinPlayers}}–{{.MaxPlayers}}</li>
+<li>Start gap: {{.StartGapHours}}h / {{.StartGapPlayers}} players</li>
+<li>Turn schedule: {{.TurnSchedule}}</li>
+<li>Target engine: {{.TargetEngineVersion}}</li>
+<li>Enrollment ends: {{.EnrollmentEndsAt}}</li>
+<li>Created: {{.CreatedAt}}</li>
+<li>Started: {{if .StartedAt}}{{.StartedAt}}{{else}}—{{end}}</li>
+<li>Finished: {{if .FinishedAt}}{{.FinishedAt}}{{else}}—{{end}}</li>
+</ul>
+{{if .Description}}<p>{{.Description}}</p>{{end}}
+<div class="actions">
+<form method="post" action="/_gm/games/{{.GameID}}/force-start" onsubmit="return confirm('Force-start this game?');"><input type="hidden" name="_csrf" value="{{$csrf}}"><button type="submit">Force start</button></form>
+<form method="post" action="/_gm/games/{{.GameID}}/force-stop" onsubmit="return confirm('Force-stop this game?');"><input type="hidden" name="_csrf" value="{{$csrf}}"><button type="submit" class="danger">Force stop</button></form>
+</div>
+</section>
+
+<section class="panel">
+<h2>Runtime</h2>
+{{if .HasRuntime}}
+<ul class="kv">
+<li>Status: {{.RuntimeStatus}}</li>
+<li>Engine version: {{.CurrentEngineVersion}}</li>
+<li>Engine health: {{.EngineHealth}}</li>
+<li>Current turn: {{.CurrentTurn}}</li>
+<li>Next generation: {{if .NextGenerationAt}}{{.NextGenerationAt}}{{else}}—{{end}}</li>
+<li>Paused: {{if .Paused}}yes{{else}}no{{end}}</li>
+</ul>
+<div class="actions">
+<form method="post" action="/_gm/games/{{.GameID}}/runtime/restart" onsubmit="return confirm('Restart the engine container?');"><input type="hidden" name="_csrf" value="{{$csrf}}"><button type="submit">Restart</button></form>
+<form method="post" action="/_gm/games/{{.GameID}}/runtime/force-next-turn" onsubmit="return confirm('Force the next turn now?');"><input type="hidden" name="_csrf" value="{{$csrf}}"><button type="submit">Force next turn</button></form>
+</div>
+<form method="post" action="/_gm/games/{{.GameID}}/runtime/patch" class="form">
+<input type="hidden" name="_csrf" value="{{$csrf}}">
+<label>Patch to version <input type="text" name="target_version" placeholder="e.g. 0.1.1" required></label>
+<button type="submit">Patch</button>
+</form>
+{{else}}
+<p class="note">No runtime record for this game yet.</p>
+{{end}}
+</section>
+
+<section class="panel">
+<h2>Ban member</h2>
+<form method="post" action="/_gm/games/{{.GameID}}/ban-member" class="form" onsubmit="return confirm('Ban this member from the game?');">
+<input type="hidden" name="_csrf" value="{{$csrf}}">
+<label>User ID <input type="text" name="user_id" required></label>
+<label>Reason <input type="text" name="reason"></label>
+<button type="submit" class="danger">Ban member</button>
+</form>
+</section>
+{{end}}
+{{- end}}