feat: multi-provider AI support with auto-detection

- Added support for Google Gemini, OpenAI, Anthropic, and Azure OpenAI
- Implemented API key validation with auto model detection
- Added Error Boundary for better error handling
- Migrated PDF generation to native jsPDF (better quality)
- Added PWA support with offline capabilities
- Implemented tests with Vitest
- Fixed language consistency (PT-BR)
- Improved accessibility (ARIA)

public/sw.js

@@ -0,0 +1,35 @@
+const CACHE_NAME = 'steelcheck-v1';
+const ASSETS = [
+  '/',
+  '/index.html',
+  '/index.tsx',
+  '/style.css'
+];
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => {
+      return cache.addAll(ASSETS);
+    })
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  event.respondWith(
+    caches.match(event.request).then((response) => {
+      return response || fetch(event.request);
+    })
+  );
+});
+
+self.addEventListener('activate', (event) => {
+  event.waitUntil(
+    caches.keys().then((cacheNames) => {
+      return Promise.all(
+        cacheNames
+          .filter((name) => name !== CACHE_NAME)
+          .map((name) => caches.delete(name))
+      );
+    })
+  );
+});