Allow all users to generate AI text for posts

Change API endpoint `/api/ai/generate` from `requireAdmin` to `requireAuth` middleware and update OpenRouterService to use shared admin configuration instead of per-user config.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: ae4037a0-2a6f-4530-9bac-79b543286bda
Replit-Commit-Checkpoint-Type: intermediate_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/397bca8c-984f-43ff-841a-10897aeb8140/ae4037a0-2a6f-4530-9bac-79b543286bda/tWDOGLP

server/storage.ts

@@ -85,6 +85,7 @@ export interface IStorage {
 
   // OpenRouter Config
   getOpenrouterConfig(userId: string): Promise<OpenrouterConfig | undefined>;
+  getAnyOpenrouterConfig(): Promise<OpenrouterConfig | undefined>;
   createOpenrouterConfig(config: InsertOpenrouterConfig): Promise<OpenrouterConfig>;
   updateOpenrouterConfig(userId: string, config: Partial<InsertOpenrouterConfig>): Promise<OpenrouterConfig>;
 
@@ -336,6 +337,11 @@ export class DatabaseStorage implements IStorage {
     return config || undefined;
   }
 
+  async getAnyOpenrouterConfig(): Promise<OpenrouterConfig | undefined> {
+    const [config] = await db.select().from(openrouterConfig).limit(1);
+    return config || undefined;
+  }
+
   async createOpenrouterConfig(config: InsertOpenrouterConfig): Promise<OpenrouterConfig> {
     const [newConfig] = await db.insert(openrouterConfig).values(config).returning();
     return newConfig;