feat(sync): le PC accepte l'adresse du depot (github.com/O/R.git, Gitea) et la convertit en URL d'API

Garde : un dernier segment qui ressemble a un fichier (.json) reste une URL
WebDAV.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

index.html

@@ -857,9 +857,9 @@
                 </label>
                 <div id="syncConfig" style="display:none;border-left:2px solid var(--border);padding-left:10px;margin-left:4px">
                     <div style="margin-bottom:6px">
-                        <div style="font-size:11px;color:var(--text-faint);margin-bottom:4px">URL — full path to the snapshot file, or a Gitea contents path</div>
+                        <div style="font-size:11px;color:var(--text-faint);margin-bottom:4px">URL — the repository address (github.com/you/repo.git or your Gitea), or a WebDAV file URL</div>
                         <input type="text" id="syncUrl" class="so-input"
-                               placeholder="https://git.example.com/api/v1/repos/OWNER/REPO/contents/vault-sync.json"
+                               placeholder="https://github.com/you/repo.git"
                                style="width:100%;font-size:12px">
                     </div>
                     <div style="display:flex;gap:8px;margin-bottom:6px">