fix: Clear .next cache and use production NODE_ENV in all contexts

The Netlify Next.js cache was restoring stale build artifacts causing
the global-error prerender failure. Now explicitly clearing .next
before each build and using NODE_ENV=production consistently.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: cj-vana

netlify.toml

@@ -61,20 +61,20 @@
   [headers.values]
     Cache-Control = "no-store, no-cache, must-revalidate"
 
-# Development/Preview context overrides
+# Preview context - clear cache to avoid stale artifacts
 [context.deploy-preview]
-  command = "npm ci && npm run build"
+  command = "rm -rf .next && npm ci && npm run build"
   [context.deploy-preview.environment]
-    NODE_ENV = "development"
+    NODE_ENV = "production"
 
 [context.branch-deploy]
-  command = "npm ci && npm run build"
+  command = "rm -rf .next && npm ci && npm run build"
   [context.branch-deploy.environment]
-    NODE_ENV = "development"
+    NODE_ENV = "production"
 
-# Production context
+# Production context - clear cache to avoid stale artifacts
 [context.production]
-  command = "npm ci && npm run build"
+  command = "rm -rf .next && npm ci && npm run build"
   [context.production.environment]
     NODE_ENV = "production"