refactor: professional code quality audit

- Fix all TypeScript compilation errors (0 errors in src/)
- Add try/catch error handling to ALL API routes (38 handlers)
- Fix empty catch blocks (api-auth.ts now logs warnings)
- Add aria-labels to all icon-only buttons (WCAG 2.1 AA)
- Fix Prisma type mismatches (OR filter, Person.companyId, Estimate.projectId, Ticket.createdAt)
- Fix webhook PATCH route (moved to [id]/route.ts)
- Fix mobile-bottom-nav type safety
- Fix KB route where-clause type
- Fix test-mail banner null vs undefined
- Fix task comment fetch: add cancellation + error toast
- ESLint: 0 errors, 0 warnings
- 175 files, 24.741 lines of code

postcss.config.mjs

@@ -0,0 +1,5 @@
+const config = {
+  plugins: ["@tailwindcss/postcss"],
+};
+
+export default config;