fix: update AI Gateway API key link (#14)

apps/web/.env.example

@@ -1,4 +1,4 @@
 # AI Gateway API Key (required for /api/generate endpoint)
 # Uses Vercel AI Gateway - automatically authenticated when deployed on Vercel
-# For local development, get your key from https://vercel.com/docs/ai/ai-sdk
+# For local development, get your key from https://vercel.com/ai-gateway
 AI_GATEWAY_API_KEY=

examples/dashboard/.env.example

@@ -1,4 +1,4 @@
 # AI Gateway API Key (required for /api/generate endpoint)
 # Uses Vercel AI Gateway - automatically authenticated when deployed on Vercel
-# For local development, get your key from https://vercel.com/docs/ai/ai-sdk
+# For local development, get your key from https://vercel.com/ai-gateway
 AI_GATEWAY_API_KEY=