feat: add share API endpoints and in-memory rate limiting

- POST/DELETE /api/notes/[id]/share for creating/revoking public links
- GET /api/shared/[token] for fetching shared note data (no auth)
- GET /api/shared/[token]/attachment/[attachmentId] for public images
- Add /s/ and /api/shared to PUBLIC_PATHS in auth middleware
- Add IP-based rate limiter (60 req/min) for public endpoints

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/hooks.server.ts

@@ -8,7 +8,9 @@ const PUBLIC_PATHS = [
 	'/setup',
 	'/api/auth/login',
 	'/api/auth/setup',
-	'/api/auth/oauth'
+	'/api/auth/oauth',
+	'/s/',
+	'/api/shared'
 ];
 
 export const handle: Handle = async ({ event, resolve }) => {