feat: implement Vue 3 frontend with all pages

Complete web UI built with Vue 3, TypeScript, Element Plus, and Pinia.
Includes Login, Dashboard, Servers, Repositories, Sync Logs, and Settings pages
with API client, auth store, and Vue Router configuration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/vite.config.ts

@@ -0,0 +1,25 @@
+import { defineConfig } from 'vite'
+import vue from '@vitejs/plugin-vue'
+import { resolve } from 'path'
+
+export default defineConfig({
+  plugins: [vue()],
+  resolve: {
+    alias: {
+      '@': resolve(__dirname, 'src')
+    }
+  },
+  server: {
+    port: 5173,
+    proxy: {
+      '/api': {
+        target: 'http://localhost:9000',
+        changeOrigin: true
+      }
+    }
+  },
+  build: {
+    outDir: 'dist',
+    assetsDir: 'assets'
+  }
+})