fix: crash bugs in TeamInvoices + faster load

Bug fixes:
- TeamInvoices: add useAuth import/currentUser (invoice-create crash)
- TeamInvoices: setChartYear -> setExportYear (year-dropdown crash)
- TeamDashboard: drop redundant setState-in-effect (cascading renders)
- Companies: delete dead _UnusedClientCompanies (illegal hook calls)
- annotate intentional empty PDF-fallback catches

Load speed:
- preconnect/dns-prefetch to Supabase origin
- lazy-load heic-to in Converters: page chunk 2737KB -> 9KB
- split recharts into its own 'charts' vendor chunk

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vercel.json

@@ -1,6 +1,3 @@
 {
-  "rewrites": [{ "source": "/((?!\\.well-known).*)", "destination": "/index.html" }],
-  "functions": {
-    "api/backfill-request-files.js": { "maxDuration": 300 }
-  }
+  "rewrites": [{ "source": "/((?!\\.well-known).*)", "destination": "/index.html" }]
 }