refactor: collapse per-env Configs into ClientEnv + ServerEnv (#3906)

## Description:

This is a refactor to simplify config handling.

Replaces the per-environment DevConfig/PreprodConfig/ProdConfig class
hierarchy with two static classes: ClientEnv (browser main thread, reads
from window.BOOTSTRAP_CONFIG) and ServerEnv (Node server, reads from
process.env). The four config classes are deleted, the abstract
DefaultServerConfig is gone, and DefaultConfig is renamed to Config.

The values that flow server → client (gameEnv, numWorkers,
turnstileSiteKey, jwtAudience, instanceId) used to be baked into the
hardcoded per-env classes. They're now real env vars on the server,
embedded into a single window.BOOTSTRAP_CONFIG object in index.html at
request time (alongside the existing gitCommit/assetManifest/cdnBase
globals, which moved into the same object), and read back by ClientEnv
on the client. The dev defaults previously hidden inside DevServerConfig
are now explicit in start:server-dev (NUM_WORKERS=2,
TURNSTILE_SITE_KEY=1x..., JWT_AUDIENCE=localhost, etc.) and in
vite.config.ts's html plugin inject.data. Production deploys plumb
NUM_WORKERS and TURNSTILE_SITE_KEY through deploy.yml (GitHub vars) into
the remote env file; JWT_AUDIENCE is derived from DOMAIN in deploy.sh.
The dynamic /api/instance endpoint is gone — INSTANCE_ID rides along in
BOOTSTRAP_CONFIG now.

ServerEnv is the only thing server code touches; ClientEnv is
browser-only. The two classes have intentional overlap (env, numWorkers,
jwtIssuer, gameCreationRate, workerIndex, etc.) since they derive
identical logic from different sources — there's a TODO in each to
consolidate via a shared helper later. The game-logic Config no longer
stores a ServerConfig/ClientEnv reference and its serverConfig() getter
is gone; the one caller (MultiTabModal) now reads ClientEnv.env()
directly. Worker init no longer carries server-config values since
nothing in the worker actually reads them.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/client/Main.ts

@@ -1,4 +1,5 @@
 import version from "resources/version.txt?raw";
+import { ClientEnv } from "src/client/ClientEnv";
 import { UserMeResponse } from "../core/ApiSchemas";
 import { assetUrl } from "../core/AssetUrls";
 import { EventBus } from "../core/EventBus";
@@ -10,7 +11,6 @@ import {
   PublicGameInfo,
 } from "../core/Schemas";
 import { GameEnv } from "../core/configuration/Config";
-import { getRuntimeClientServerConfig } from "../core/configuration/ConfigLoader";
 import { GameType } from "../core/game/Game";
 import {
   DARK_MODE_KEY,
@@ -169,7 +169,6 @@ function updateAccountNavButton(userMeResponse: UserMeResponse | false) {
 
 declare global {
   interface Window {
-    GIT_COMMIT: string;
     turnstile: any;
     adsEnabled: boolean;
     PageOS: {
@@ -770,16 +769,14 @@ class Client {
     if (lobby.source === "public") {
       this.joinModal?.open(lobby.gameID, lobby.publicLobbyInfo);
     }
-    const config = await getRuntimeClientServerConfig();
     // Only update URL immediately for private lobbies, not public ones
     if (lobby.source !== "public") {
-      this.updateJoinUrlForShare(lobby.gameID, config);
+      this.updateJoinUrlForShare(lobby.gameID);
     }
     const auth = await userAuth();
     const playerRole = auth !== false ? (auth.claims.role ?? null) : null;
     const newLobbyHandle = joinLobby(this.eventBus, {
       gameID: lobby.gameID,
-      serverConfig: config,
       cosmetics: await getPlayerCosmeticsRefs(),
       turnstileToken: await this.getTurnstileToken(lobby),
       playerName: this.usernameInput?.getUsername() ?? genAnonUsername(),
@@ -881,7 +878,7 @@ class Client {
         "",
         lobbyIdHidden
           ? "/streamer-mode"
-          : `/${config.workerPath(lobby.gameID)}/game/${lobby.gameID}?live`,
+          : `/${ClientEnv.workerPath(lobby.gameID)}/game/${lobby.gameID}?live`,
       );
 
       // Store current URL for popstate confirmation
@@ -889,14 +886,11 @@ class Client {
     });
   }
 
-  private updateJoinUrlForShare(
-    lobbyId: string,
-    config: Awaited<ReturnType<typeof getRuntimeClientServerConfig>>,
-  ) {
+  private updateJoinUrlForShare(lobbyId: string) {
     const lobbyIdHidden = !this.userSettings.lobbyIdVisibility();
     const targetUrl = lobbyIdHidden
       ? "/streamer-mode"
-      : `/${config.workerPath(lobbyId)}/game/${lobbyId}`;
+      : `/${ClientEnv.workerPath(lobbyId)}/game/${lobbyId}`;
     const currentUrl = window.location.pathname;
 
     if (currentUrl !== targetUrl) {
@@ -970,9 +964,8 @@ class Client {
   private async getTurnstileToken(
     lobby: JoinLobbyEvent,
   ): Promise<string | null> {
-    const config = await getRuntimeClientServerConfig();
     if (
-      config.env() === GameEnv.Dev ||
+      ClientEnv.env() === GameEnv.Dev ||
       lobby.gameStartInfo?.config.gameType === GameType.Singleplayer
     ) {
       return null;
@@ -1048,9 +1041,8 @@ async function getTurnstileToken(): Promise<{
     throw new Error("Failed to load Turnstile script");
   }
 
-  const config = await getRuntimeClientServerConfig();
   const widgetId = window.turnstile.render("#turnstile-container", {
-    sitekey: config.turnstileSiteKey(),
+    sitekey: ClientEnv.turnstileSiteKey(),
     size: "normal",
     appearance: "interaction-only",
     theme: "light",