feat: complete auth and gateway agnostic billing implementation

src/app/login/page.tsx

@@ -29,10 +29,23 @@ export default function LoginPage() {
       const data = await res.json()
 
       if (data.success) {
-        if (data.role === "admin") {
-          router.push("/admin")
-        } else {
-          router.push("/dashboard")
+        if (typeof window !== "undefined") {
+          localStorage.setItem("activeUserId", data.token)
+          // Create new session token for single-device login
+          const sessionToken = crypto.randomUUID();
+          localStorage.setItem("active_session_token", sessionToken);
+          
+          fetch(`/api/users/${data.token}/session`, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ session_token: sessionToken })
+          }).finally(() => {
+            if (data.role === "admin") {
+              window.location.href = "/admin";
+            } else {
+              window.location.href = "/dashboard";
+            }
+          });
         }
       } else {
         setError(data.error || "Invalid email or password.")
@@ -76,7 +89,7 @@ export default function LoginPage() {
                   <label className="text-sm font-bold text-foreground">
                     Password
                   </label>
-                  <Link href="#" className="text-xs font-bold text-[#00F0FF] hover:text-[#00F0FF]/80 transition-colors">Forgot password?</Link>
+                  <Link href="/forgot-password" className="text-xs font-bold text-[#00F0FF] hover:text-[#00F0FF]/80 transition-colors">Forgot password?</Link>
                 </div>
                 <div className="relative">
                   <input