feat: add WannPassts booking app with Go backend and Vue frontend

Initial project setup for a privacy-focused, self-hosted scheduling app:

- Go backend with JWT auth, SQLite storage, and chi router
- Calendar integrations via Google OAuth (FreeBusy), CalDAV, and ICS links
- Public booking pages with configurable slots and booking requests
- AES-256-GCM encryption for stored provider tokens
- Vue 3 + TypeScript frontend with Vite, Pinia, and Vue Router
- Docs, .gitignore, and .env.example for local development

frontend/public/favicon.svg

@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 48 48">
+  <defs>
+    <linearGradient id="g" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0" stop-color="#7db0ff"/>
+      <stop offset="1" stop-color="#b78cff"/>
+    </linearGradient>
+  </defs>
+  <rect x="4" y="6" width="40" height="38" rx="11" fill="#0b0f1a" stroke="url(#g)" stroke-width="2.5"/>
+  <rect x="4" y="6" width="40" height="10" rx="5" fill="url(#g)" opacity="0.35"/>
+  <path d="M15 3.5v6M33 3.5v6" stroke="url(#g)" stroke-width="3" stroke-linecap="round"/>
+  <path d="M15 26.5l6 6 12-12" stroke="url(#g)" stroke-width="4" stroke-linecap="round" stroke-linejoin="round" fill="none"/>
+</svg>