refactor(clone-dialog): generalize repository grouping and support gitea

Generalize the repository grouping logic so grouping is driven by a single
derived flag and not tied to a single provider. Replace the Azure-specific
group variable with a generic repositoryGroups value and use a shared
usesRepositoryGroups switch so grouping can be enabled for other providers.

- Add usesRepositoryGroups derived flag to centralize grouping logic
- Replace azure-only grouping with repositoryGroups and enable Gitea grouping

src/lib/components/CloneRepositoryDialog.svelte

@@ -64,8 +64,9 @@
     if (!query) return activeRepositories;
     return activeRepositories.filter((repository) => `${repository.fullName} ${repository.description}`.toLocaleLowerCase().includes(query));
   });
-  const azureRepositoryGroups = $derived.by(() => {
-    if (activeSource?.provider !== "azure-devops") return [];
+  const usesRepositoryGroups = $derived(activeSource?.provider === "azure-devops" || activeSource?.provider === "gitea");
+  const repositoryGroups = $derived.by(() => {
+    if (!usesRepositoryGroups) return [];
     const groups = new Map<string, GitIntegrationRepository[]>();
     for (const repository of filteredRepositories) {
       const separator = repository.fullName.indexOf("/");
@@ -390,8 +391,8 @@
                   <div class="repository-state repository-state-error"><strong>{isGerman ? "Repositories konnten nicht geladen werden" : "Could not load repositories"}</strong><span>{repositoryError}</span></div>
                 {:else if filteredRepositories.length === 0}
                   <div class="repository-state"><GitBranch size={20} /><span>{repositorySearch ? (isGerman ? "Keine passenden Repositories." : "No matching repositories.") : (isGerman ? "Keine Repositories gefunden." : "No repositories found.")}</span></div>
-                {:else if activeSource?.provider === "azure-devops"}
-                  {#each azureRepositoryGroups as group (group.project)}
+                {:else if usesRepositoryGroups}
+                  {#each repositoryGroups as group (group.project)}
                     <section class="repository-project-group" aria-label={group.project}>
                       <div class="repository-project-header"><span>{group.project}</span><em>{group.repositories.length}</em></div>
                       {#each group.repositories as repository (repository.id)}