fix: make STEAM_API_KEY optional so the proxy starts without it

The proxy now boots without a key; /items routes still return 500 when a key is required but missing.

apps/proxy/src/env.test.ts

@@ -16,8 +16,8 @@ describe('loadEnv', () => {
     });
   });
 
-  it('throws when STEAM_API_KEY is missing', () => {
-    expect(() => loadEnv({})).toThrow(/STEAM_API_KEY/);
+  it('allows a missing STEAM_API_KEY', () => {
+    expect(loadEnv({})).toEqual({ PORT: 3000 });
   });
 
   it('throws on an invalid PORT', () => {

apps/proxy/src/env.ts

@@ -1,7 +1,7 @@
 import { z } from 'zod';
 
 const envSchema = z.object({
-  STEAM_API_KEY: z.string().min(1, 'STEAM_API_KEY is required'),
+  STEAM_API_KEY: z.string().min(1).optional(),
   PORT: z.coerce.number().int().min(1).max(65535).default(3000),
 });
 
@@ -9,7 +9,7 @@ export type Env = z.infer<typeof envSchema>;
 
 /** Hono bindings type so `c.env` is typed in route handlers. */
 export interface Bindings {
-  STEAM_API_KEY: string;
+  STEAM_API_KEY?: string;
   PORT: number;
 }