feat(settings): split General into pages; collapse the big pickers (#459, #460)

#459 General held 76 of ~110 settings (11 screens). Its sections now live
on pages named for what people come to do:
  Account, Appearance, Messages (incl. editor, date and time),
  Notifications, Calls & audio, Privacy & security (privacy options +
  the former Devices page), Data & storage (storage, sync, your data),
  Desktop (desktop app only), Emojis & stickers, Advanced (the former
  Developer Tools + "show hidden events" / "legacy username colour"),
  About.
The longest page is now ~3 screens (Appearance). Settings opens on
Account. Deep links keep working: "devices" lands on Privacy & security,
the old "general" on Appearance, the update notice on Desktop. Text that
pointed at the old page names is updated. The push-rule editor gets one
line explaining the Matrix terms. Remaining Title Case labels on Account
and Devices are sentence case.

#460 Chat background, seasonal theme and avatar decoration grids sit
behind one row: the current choice and a Change button (the first two
close after a choice; decorations keep their Save step).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

e2e/a11y.spec.ts-snapshots/settings-nav.aria.yml

@@ -1,22 +1,31 @@
 - navigation "Settings sections":
-    - button "General" [pressed]:
-        - img
-        - paragraph: General
-    - button "Account":
+    - button "Account" [pressed]:
         - img
         - paragraph: Account
+    - button "Appearance":
+        - img
+        - paragraph: Appearance
+    - button "Messages":
+        - img
+        - paragraph: Messages
     - button "Notifications":
         - img
         - paragraph: Notifications
-    - button "Devices":
+    - button "Calls & audio":
         - img
-        - paragraph: Devices
-    - button "Emojis & Stickers":
+        - paragraph: Calls & audio
+    - button "Privacy & security":
         - img
-        - paragraph: Emojis & Stickers
-    - button "Developer Tools":
+        - paragraph: Privacy & security
+    - button "Data & storage":
         - img
-        - paragraph: Developer Tools
+        - paragraph: Data & storage
+    - button "Emojis & stickers":
+        - img
+        - paragraph: Emojis & stickers
+    - button "Advanced":
+        - img
+        - paragraph: Advanced
     - button "About":
         - img
         - paragraph: About

e2e/key-upload-recovery.spec.ts

@@ -31,7 +31,7 @@ test.describe('key upload recovery (#201)', () => {
     expect(rejected).toBeGreaterThanOrEqual(3);
 
     await banner.getByRole('button', { name: 'Details' }).click();
-    await expect(banner).toContainText('Settings → Devices');
+    await expect(banner).toContainText('Settings → Privacy & security');
     await expect(banner).toContainText('already exists');
 
     await banner.getByRole('button', { name: /Fix: sign out/ }).click();

e2e/security-nudge.spec.ts

@@ -75,7 +75,9 @@ test.describe('security nudge (#110, #123)', () => {
     await expect(strip(page)).toHaveCount(0);
   });
 
-  test('no key backup: "Set up key backup" opens Settings → Devices', async ({ page }) => {
+  test('no key backup: "Set up key backup" opens Settings → Privacy & security', async ({
+    page,
+  }) => {
     test.setTimeout(150_000);
     await loginUI(page, user);
     await pastGrace(page);

e2e/your-data.spec.ts

@@ -39,7 +39,7 @@ test.describe('your data (#114)', () => {
       .catch(() => undefined);
     const openGeneral = async () => {
       await page.getByRole('button', { name: 'User Settings' }).click();
-      await page.getByRole('dialog').getByText('General', { exact: true }).first().click();
+      await page.getByRole('dialog').getByText('Data & storage', { exact: true }).first().click();
       await page
         .getByRole('dialog')
         .getByText('Your data', { exact: true })