fix(frontend): darken light-theme page bg so cards stand out

The light-theme --bg-page was #f0f2f5 — close enough to AD-Vue's #fff
card background that the cards faded into the page. Bump it to #e6e8ec
(a more visibly distinct gray) so cards lift cleanly off the surface.
Dark and ultra-dark stay where they were.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/pages/inbounds/InboundsPage.vue

@@ -669,7 +669,7 @@ function onRowAction({ key, dbInbound }) {
 
 <style scoped>
 .inbounds-page {
-  --bg-page: #f0f2f5;
+  --bg-page: #e6e8ec;
   --bg-card: #ffffff;
 
   min-height: 100vh;

frontend/src/pages/index/IndexPage.vue

@@ -319,7 +319,7 @@ async function openConfig() {
 
 <style scoped>
 .index-page {
-  --bg-page: #f0f2f5;
+  --bg-page: #e6e8ec;
   --bg-card: #ffffff;
 
   min-height: 100vh;

frontend/src/pages/settings/SettingsPage.vue

@@ -250,7 +250,7 @@ const alertVisible = ref(true);
 
 <style scoped>
 .settings-page {
-  --bg-page: #f0f2f5;
+  --bg-page: #e6e8ec;
   --bg-card: #ffffff;
 
   min-height: 100vh;

frontend/src/pages/xray/XrayPage.vue

@@ -301,7 +301,7 @@ function confirmRestart() {
 
 <style scoped>
 .xray-page {
-  --bg-page: #f0f2f5;
+  --bg-page: #e6e8ec;
   --bg-card: #ffffff;
 
   min-height: 100vh;