fix(studio): theme picker confirms applied + surfaces load failures

Two operator-visible fixes prompted by 'I picked a theme but
nothing changed':

  - Theme picker tile taps now show a brief "Theme applied:
    <name>" snackbar — the picker applies themes instantly, so
    the operator needs a confirming cue. Slow `_pluginThemes`
    loads no longer read as "click did nothing".
  - `_pluginThemes` failures (plugin unreachable, manifest
    drift, etc.) write to `FaiLog` so `fai admin doctor` and
    Studio's inline log viewer can surface them. Previously
    swallowed silently, which is what made debugging this so
    miserable.
  - Settings dialog's primary button relabelled to
    "Connect to endpoint" (was "Save & connect") so operators
    don't mistake it for "save my theme choice". The theme
    selection persists at tile-tap time; the Settings dialog
    has nothing left to "save".
  - Theme section header gains an explicit "(applies instantly)"
    cue for the same reason.

Also fixes a pre-existing curly-braces lint in the n8n add-
endpoint dialog. Studio bumped to 0.62.1, editor pinned via
path override at 0.15.1.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/main.dart

@@ -8,6 +8,7 @@ import 'dart:async';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 
+import 'data/fai_log.dart';
 import 'data/hub.dart';
 import 'data/system_actions.dart';
 import 'data/theme_plugin.dart';
@@ -26,7 +27,7 @@ import 'widgets/widgets.dart';
 /// Studio's own build version. Bump on every UI commit so the
 /// running app self-identifies — visible in the sidebar header
 /// and quick-glance proof that you're seeing the current build.
-const String kStudioVersion = '0.62.0';
+const String kStudioVersion = '0.62.1';
 
 Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
@@ -178,10 +179,18 @@ class StudioAppState extends State<StudioApp> {
             : themeDataFromScheme(schemes.light!),
         dark: schemes.dark == null ? null : themeDataFromScheme(schemes.dark!),
       );
-    } catch (_) {
-      // Plugin unreachable, hub down, etc. Fall back to
-      // FaiTheme defaults silently — the Settings dialog is
-      // where the operator surfaces / fixes the problem.
+    } catch (e) {
+      // Plugin unreachable, hub down, manifest schema drift —
+      // any of these end up here. Log the failure so doctor +
+      // the in-app log viewer can surface it; the picker's
+      // own "applied" snackbar is replaced upstream by the
+      // friendlier failure message via [themePluginFailed].
+      // ignore: discarded_futures
+      FaiLog.instance.error(
+        'theme.plugin.load',
+        e,
+        context: 'capability=$capability',
+      );
       return (light: null, dark: null);
     }
   }