fix: scope Alpine gitea_workspace + commit admin fallback + settings cleanup

1. gitea_workspace.html: owner/repo en Jinja2 dans la topbar (pas Alpine)
2. gitea.py: save_file/delete_file → _require_gitea (admin token can write)
3. settings.html: retrait doublon defaultView, fix workspace_name Jinja2

app/templates/gitea_workspace.html

@@ -9,7 +9,7 @@
   </button>
   <div class="topbar-left">
     <a href="/workspaces" class="breadcrumb" style="color:rgba(255,255,255,.5);text-decoration:none;">Home</a>
-    <span class="page-title-topbar" x-text="owner + '/' + repo"></span>
+    <span class="page-title-topbar">{{ owner }}/{{ repo }}</span>
   </div>
   <div class="topbar-right">
     <button class="page-action-btn" @click="refreshTree()" title="Refresh">🔄</button>