refactor(credentials): remove credential expiry support and API

The credential expiry feature has been removed from both the Rust
backend and the frontend. Stored credentials now include only
username and password.

- Remove expiresAt field from StoredCredential
- Simplify API by removing expiry param from credSave
- Drop expiry UI and expiry checks across the app

src/App.svelte

@@ -180,7 +180,6 @@
 
   import {
     orgKeyFromUrl,
-    isCredentialExpired,
     isAuthError,
     stripAuthPrefix,
     summarizeGitError,
@@ -2219,11 +2218,10 @@
 
     if (!username && !password) {
       const stored = await loadStoredCredential(credentialKey);
-      if (stored && !isCredentialExpired(stored)) {
+      if (stored) {
         await cloneRepo(remoteUrl, parentPath, directoryName, stored.username, stored.password, credentialKey, true);
         return;
       }
-      if (stored && credentialKey) await credDelete(credentialKey).catch(() => {});
     }
 
     operation = "Cloning repository";
@@ -2921,7 +2919,7 @@
     if (!activeRepoPath || isBusy) return;
     const key = await currentCredKey();
     const stored = await loadStoredCredential(key);
-    const credential = stored && !isCredentialExpired(stored) ? stored : null;
+    const credential = stored ?? null;
 
     await runOperation(`Pushing tag ${tag.name}`, async () => {
       try {
@@ -3028,12 +3026,7 @@
   async function storedCredentialForNoteRemote(remote: string, direction: "fetch" | "push") {
     const config = commitNoteRemotes.find((item) => item.name === remote);
     const key = orgKeyFromUrl(direction === "push" ? (config?.push_url ?? "") : (config?.fetch_url ?? ""));
-    const stored = await loadStoredCredential(key);
-    if (stored && isCredentialExpired(stored)) {
-      if (key) await credDelete(key).catch(() => {});
-      return null;
-    }
-    return stored;
+    return loadStoredCredential(key);
   }
 
   function commitNoteRemoteError(error: unknown): string {
@@ -3271,12 +3264,7 @@
     handleRemoteResult("push", key, fromStore);
   }
 
-  async function handleCredentialSubmit(
-    username: string,
-    password: string,
-    save: boolean,
-    expiresAt: string | null,
-  ) {
+  async function handleCredentialSubmit(username: string, password: string, save: boolean) {
     const key = credDialogKey;
     if (credDialogAction === "pull") await doActualPull(username, password, key, false);
     else if (credDialogAction === "push") await doActualPush(username, password, key, false);
@@ -3296,7 +3284,7 @@
     // Only persist once the operation actually succeeded (dialog has closed).
     if (!credDialogOpen && save && key) {
       try {
-        await credSave(key, username, password, expiresAt);
+        await credSave(key, username, password);
       } catch (error) {
         errorMessage = errorToMessage(error);
       }
@@ -3311,15 +3299,13 @@
     const key = await currentCredKey();
     const stored = await loadStoredCredential(key);
 
-    if (stored && !isCredentialExpired(stored)) {
+    if (stored) {
       if (action === "pull") await doActualPull(stored.username, stored.password, key, true);
       else if (action === "fetch") await doActualFetch(stored.username, stored.password, key, true);
       else await doActualPush(stored.username, stored.password, key, true);
       return;
     }
 
-    // Expired entry → clean it up before prompting again.
-    if (stored && key) await credDelete(key).catch(() => {});
     await openCredentialDialog(action, key);
   }