feat(integrations): add Git hosting integrations and repo listing

Add support for integrating with external Git hosts (GitLab, Gitea,
and Azure DevOps). The backend gains a client to fetch paginated
repository lists, normalise base URLs, and surface provider errors.
Credentials are loaded from the OS keychain and a Tauri command is
exposed for the frontend to list integration repositories.

- Implement integration client with pagination, deserialization,
  and provider-specific handling.
- Centralise keychain credential loading and expose listing command.
- Update UI to manage integration metadata, persist settings, and
  save/remove tokens to the OS keychain for cloning and operations.

src/App.svelte

@@ -117,6 +117,7 @@
     launchExternalMerge,
     launchExternalTool,
     credLoad,
+    credDelete,
     credSave,
     getFilePatch,
     readConflict,
@@ -158,6 +159,9 @@
     ExplorerNodeKind,
     ExternalDiffScope,
     ExternalToolsSettings,
+    GitIntegrationSecretUpdate,
+    GitIntegrationSettings,
+    GitIntegrationProvider,
     GitBlameLine,
     GitBranch as GitBranchInfo,
     GitCommit,
@@ -190,6 +194,11 @@
     normaliseExternalToolsSettings,
     resolveDetectedExternalToolPrograms,
   } from "./lib/externalTools";
+  import {
+    defaultGitIntegrationSettings,
+    integrationCredentialKey,
+    normaliseGitIntegrationSettings,
+  } from "./lib/integrations";
 
   import {
     orgKeyFromUrl,
@@ -259,6 +268,7 @@
   const CUSTOM_THEME_KEY = "gitlite.customTheme.v1";
   const APP_LANGUAGE_KEY = "gitlite.language.v1";
   const EXTERNAL_TOOLS_SETTINGS_KEY = "gitlite.externalTools.v1";
+  const GIT_INTEGRATIONS_SETTINGS_KEY = "gitlite.integrations.v1";
   const AUTO_REFRESH_ENABLED_KEY = "gitlite.autoRefreshEnabled.v1";
   const COMMIT_PANEL_HEIGHT_KEY = "gitlite.commitPanelHeight.v1";
   const LEFT_SIDEBAR_WIDTH_KEY = "gitlite.leftSidebarWidth.v1";
@@ -372,6 +382,7 @@
   let customTheme: CustomThemeColors = loadCustomTheme();
   let appLanguage: AppLanguage = loadLanguagePreference();
   let externalToolsSettings: ExternalToolsSettings = loadExternalToolsSettings();
+  let gitIntegrationSettings: GitIntegrationSettings = loadGitIntegrationSettings();
   let externalToolsConfigured = hasStoredExternalToolsSettings();
   let detectedExternalTools: DetectedExternalTool[] = [];
   let externalToolsDetectionPending = true;
@@ -1260,7 +1271,33 @@
     if (appTheme === "system") applyThemePreference(appTheme);
   }
 
-  function saveAppSettings(next: AnalyticsSettings, nextTheme: AppTheme, nextAppearance: AppAppearance, nextCustomTheme: CustomThemeColors, nextLanguage: AppLanguage, nextAutoRefresh: boolean, nextExternalTools: ExternalToolsSettings) {
+  async function saveAppSettings(next: AnalyticsSettings, nextTheme: AppTheme, nextAppearance: AppAppearance, nextCustomTheme: CustomThemeColors, nextLanguage: AppLanguage, nextAutoRefresh: boolean, nextExternalTools: ExternalToolsSettings, nextIntegrations: GitIntegrationSettings, integrationSecrets: GitIntegrationSecretUpdate[]) {
+    const integrationsToSave = structuredClone(nextIntegrations);
+    try {
+      for (const update of integrationSecrets) {
+        const key = integrationCredentialKey(update.provider, update.accountId);
+        const azureOrganization = update.provider === "azure-devops" && update.accountId
+          ? integrationsToSave.azureDevOpsOrganizations.find((organization) => organization.id === update.accountId)
+          : undefined;
+        const providerConfig = integrationsToSave.providers[update.provider];
+        if (update.removeToken) {
+          await credDelete(key);
+          if (azureOrganization) azureOrganization.tokenStored = false;
+          else providerConfig.tokenStored = false;
+        } else if (update.token) {
+          const username = (azureOrganization?.username ?? providerConfig.username).trim() || "oauth2";
+          await credSave(key, username, update.token, "token");
+          if (azureOrganization) azureOrganization.tokenStored = true;
+          else providerConfig.tokenStored = true;
+        }
+      }
+    } catch (error) {
+      errorMessage = appLanguage === "de"
+        ? `Integration konnte nicht gespeichert werden: ${String(error)}`
+        : `Could not save integration: ${String(error)}`;
+      return;
+    }
+
     const autoRefreshWasEnabled = autoRefreshEnabled;
     analyticsSettings = next;
     appTheme = nextTheme;
@@ -1269,12 +1306,14 @@
     appLanguage = nextLanguage;
     autoRefreshEnabled = nextAutoRefresh;
     externalToolsSettings = nextExternalTools;
+    gitIntegrationSettings = integrationsToSave;
     persistAnalyticsSettings(next);
     persistThemePreference(nextTheme);
     persistAppearancePreference(nextAppearance, nextCustomTheme);
     persistLanguagePreference(nextLanguage);
     persistStoredBoolean(AUTO_REFRESH_ENABLED_KEY, nextAutoRefresh);
     persistExternalToolsSettings(nextExternalTools);
+    persistGitIntegrationSettings(integrationsToSave);
     externalToolsConfigured = true;
     setTelemetryEnabled(next.enabled);
     appSettingsOpen = false;
@@ -2578,6 +2617,11 @@
     trackEvent("clone_dialog_opened");
   }
 
+  function cloneFromDialog(remoteUrl: string, parentPath: string, directoryName: string, provider?: GitIntegrationProvider, accountId?: string) {
+    const credentialKey = provider ? integrationCredentialKey(provider, accountId) : undefined;
+    void cloneRepo(remoteUrl, parentPath, directoryName, undefined, undefined, credentialKey, false, provider ? "token" : "credentials");
+  }
+
   function openRepoManagement() {
     if (isBusy) return;
     activeView = "management";
@@ -4587,6 +4631,22 @@
     }
   }
 
+  function loadGitIntegrationSettings(): GitIntegrationSettings {
+    try {
+      return normaliseGitIntegrationSettings(JSON.parse(localStorage.getItem(GIT_INTEGRATIONS_SETTINGS_KEY) ?? "null"));
+    } catch {
+      return defaultGitIntegrationSettings();
+    }
+  }
+
+  function persistGitIntegrationSettings(next: GitIntegrationSettings) {
+    try {
+      localStorage.setItem(GIT_INTEGRATIONS_SETTINGS_KEY, JSON.stringify(next));
+    } catch {
+      // Metadata persistence is best-effort; tokens remain in the OS keychain.
+    }
+  }
+
   function hasStoredExternalToolsSettings(): boolean {
     try {
       return localStorage.getItem(EXTERNAL_TOOLS_SETTINGS_KEY) != null;
@@ -5710,6 +5770,7 @@
     language={appLanguage}
     autoRefresh={autoRefreshEnabled}
     externalTools={externalToolsSettings}
+    integrations={gitIntegrationSettings}
     detectedTools={detectedExternalTools}
     detectionPending={externalToolsDetectionPending}
     detectionUnavailable={externalToolsDetectionUnavailable}
@@ -6043,7 +6104,9 @@
   <CloneRepositoryDialog
     isBusy={operation === "Cloning repository"}
     error={cloneDialogError}
-    onClone={cloneRepo}
+    language={appLanguage}
+    integrations={gitIntegrationSettings}
+    onClone={cloneFromDialog}
     onClose={() => { if (!isBusy) cloneDialogOpen = false; }}
   />
 {/if}