preserve client session after partial load failure

src/App.svelte

@@ -350,7 +350,10 @@
         headers: { 'content-type': 'application/json' },
         body: JSON.stringify({ username, password }),
       });
-      if (!response.ok) throw new Error('Your username or password may be incorrect.');
+      if (!response.ok) {
+        const failure = (await response.json().catch(() => undefined)) as { message?: string; code?: string } | undefined;
+        throw new Error(failure?.message || failure?.code || 'The server could not process the login.');
+      }
       const result: { session_token: string; must_replace_credentials: boolean } = await response.json();
       sessionToken = result.session_token;
       authenticated = true;
@@ -359,7 +362,11 @@
         authError = 'Login succeeded, but the session could not be stored in the Linux keyring.';
       });
       connectionState = 'CONNECTED';
-      await loadAuthenticatedData();
+      try {
+        await loadAuthenticatedData();
+      } catch {
+        authError = 'Login succeeded, but some dashboard data could not be loaded.';
+      }
       if (!mustReplaceCredentials) password = '';
       if (mustReplaceCredentials) newUsername = username;
     } catch (error) {