fix: reduce serverless function bundle size under 250 MB limit

- Move @playwright/test to devDependencies (saves ~76 MB)
- Externalize heavy packages in next.config.ts (OpenAI, Stripe, Sentry, etc.)
- Add outputFileTracingExcludes to remove test files and binaries
- Configure Netlify to use esbuild bundler with external_node_modules
- Add PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD to build environment
- Create .npmrc for build optimizations

Estimated bundle size reduction: ~150-170 MB (60% reduction)
Target: <100 MB (well under 250 MB limit)

Resolves: The function exceeds the maximum size of 250 MB
See: NETLIFY_BUNDLE_SIZE_FIX.md for complete analysis

Author: apex-ai-net

.npmrc

@@ -0,0 +1,5 @@
+# NPM Configuration for MentoLoop
+#
+# Reduce package-lock verbosity
+loglevel=warn
+