feat: Add /login and /signup pages that initiate OAuth flow

app/login/page.tsx

@@ -0,0 +1,18 @@
+'use client'
+
+import { useEffect } from 'react'
+import { initiateOAuthFlow } from '@/lib/api/oauth'
+import LoadingOverlay from '@/components/LoadingOverlay'
+
+export default function LoginPage() {
+  useEffect(() => {
+    // * Immediately initiate OAuth flow when page loads
+    initiateOAuthFlow()
+  }, [])
+
+  return (
+    <LoadingOverlay 
+      title="Redirecting to sign in..."
+    />
+  )
+}

app/signup/page.tsx

@@ -0,0 +1,19 @@
+'use client'
+
+import { useEffect } from 'react'
+import { initiateOAuthFlow } from '@/lib/api/oauth'
+import LoadingOverlay from '@/components/LoadingOverlay'
+
+export default function SignupPage() {
+  useEffect(() => {
+    // * Immediately initiate OAuth flow when page loads
+    // * The auth service will handle showing signup vs login
+    initiateOAuthFlow()
+  }, [])
+
+  return (
+    <LoadingOverlay 
+      title="Redirecting to sign up..."
+    />
+  )
+}