Support Webshare guest downloads without login.

Credentials optional: empty WEBSHARE_* uses file_link without wst (free CDN). Verified against live API; docs and tests updated. Includes cancel→dequeue fix for queued downloads.

__tests__/webshare.test.js

@@ -16,6 +16,44 @@ describe('WebshareClient', () => {
     client = new WebshareClient('user', 'pass');
   });
 
+  describe('guest mode', () => {
+    it('marks guest when username/password missing', () => {
+      expect(new WebshareClient('', '').guest).toBe(true);
+      expect(new WebshareClient(undefined, undefined).guest).toBe(true);
+      expect(new WebshareClient('u', '').guest).toBe(true);
+      expect(new WebshareClient('', 'p').guest).toBe(true);
+      expect(new WebshareClient('u', 'p').guest).toBe(false);
+    });
+
+    it('ensureAuth is a no-op in guest mode', async () => {
+      const guest = new WebshareClient('', '');
+      await guest.ensureAuth();
+      expect(axios.post).not.toHaveBeenCalled();
+      expect(guest.wst).toBeNull();
+    });
+
+    it('getFileLink works without login and omits wst', async () => {
+      const guest = new WebshareClient();
+      mockResponse({ status: 'OK', link: 'https://free.1.dl.wsfiles.cz/file.mkv' });
+      const link = await guest.getFileLink('identGuest');
+      expect(link).toBe('https://free.1.dl.wsfiles.cz/file.mkv');
+      expect(axios.post).toHaveBeenCalledTimes(1);
+      const [url, body] = axios.post.mock.calls[0];
+      expect(url).toContain('file_link');
+      const params = new URLSearchParams(body);
+      expect(params.get('ident')).toBe('identGuest');
+      expect(params.get('wst')).toBeNull();
+      expect(params.get('download_type')).toBe('file_download');
+    });
+
+    it('getFileLink does not re-login when guest request fails', async () => {
+      const guest = new WebshareClient('', '');
+      mockResponse({ status: 'FATAL', message: 'File not found' });
+      await expect(guest.getFileLink('missing')).rejects.toThrow('file_link() FATAL: File not found');
+      expect(axios.post).toHaveBeenCalledTimes(1);
+    });
+  });
+
   // ── ensureAuth / _login ─────────────────────────────────────────────────
 
   describe('ensureAuth()', () => {
@@ -157,7 +195,7 @@ describe('WebshareClient', () => {
       mockResponse({ status: 'OK', salt: 'salt123a' });
       mockResponse({ status: 'OK', token: 'tok2' });
       mockResponse({ status: 'FATAL', message: 'File unavailable' });
-      await expect(client.getFileLink('badident')).rejects.toThrow('file_link() failed: File unavailable');
+      await expect(client.getFileLink('badident')).rejects.toThrow('file_link() FATAL: File unavailable');
     });
 
     it('calls ensureAuth before requesting link', async () => {