refactor(api): remove AI worker, add ai api route, add usage tiers

- Remove separate AI worker service
- Added generation limits:
  FREE: 1000/month (For the beta version)
  PRO: 500/month
  ENTERPRISE: 1000/month
- Integrate AI functionality into main API routes
- Added monthly generations reset and usage tier upgrade API routes
- Upgrade tier page to be added along with profile page section

frontend/app/api/user/upgrade-tier/route.ts

@@ -0,0 +1,42 @@
+import { currentUser } from "@clerk/nextjs"
+
+export async function POST(request: Request) {
+  try {
+    const user = await currentUser()
+    if (!user) {
+      return new Response("Unauthorized", { status: 401 })
+    }
+
+    const { tier } = await request.json()
+    
+    // handle payment processing here
+        
+    const response = await fetch(
+      `${process.env.NEXT_PUBLIC_DATABASE_WORKER_URL}/api/user/update-tier`,
+      {
+        method: "POST",
+        headers: {
+          Authorization: `${process.env.NEXT_PUBLIC_WORKERS_KEY}`,
+          "Content-Type": "application/json",
+        },
+        body: JSON.stringify({
+          userId: user.id,
+          tier,
+          tierExpiresAt: new Date(Date.now() + 30 * 24 * 60 * 60 * 1000), // 30 days
+        }),
+      }
+    )
+
+    if (!response.ok) {
+      throw new Error("Failed to upgrade tier")
+    }
+
+    return new Response("Tier upgraded successfully")
+  } catch (error) {
+    console.error("Tier upgrade error:", error)
+    return new Response(
+      error instanceof Error ? error.message : "Internal Server Error",
+      { status: 500 }
+    )
+  }
+}