feat(mobile): unify welcome and recent homes, add HarmonyOS offline MiniApps

[wgqqqqq]

Summary

Unify the native mobile entry experience with an animated welcome page, brand launch reveal and a recent-session home. HarmonyOS also gains bundled offline MiniApps and responsive welcome layouts for foldable screens.

• Replace redundant disconnected landing surfaces while retaining both account login and sign-in-free QR connection. Improve offline account error copy.
• Show up to three recent, non-archived sessions with device/workspace context. Keep session creation in workspace navigation and remove the redundant home browse button.
• Add native brand motion and shared design tokens for HarmonyOS, Android and iOS. HarmonyOS switches between compact, centered and side-by-side welcome layouts using current window geometry.
• Bundle HarmonyOS MiniApps for offline use, present them as a preview library, fix mobile divination scrolling, and keep sidebar destinations within the closing animation.

Type and Areas

Type: Feature / bug fix / UI/UX

Areas: Native mobile (HarmonyOS, Android, iOS), mobile design system, account presentation, HarmonyOS MiniApps.

Motivation / Impact

Signed-out users can log in or scan to connect without encountering duplicate device/login panels. Signed-in users return to recent work with explicit device and workspace context. A fully expanded triple-fold screen uses a constrained two-column welcome composition instead of stretching a phone layout or leaving an empty workspace sidebar.

Verification

• pnpm run mobile:ui:check — passed.
• pnpm run mobile:architecture — passed.
• pnpm run theme:color-audit:all — all 23 selected surfaces passed.
• HarmonyOS: node --test miniapps/*.test.cjs — passed; assembleHap and local unit tests through hvigor — passed.
• Android: ./gradlew :app:assembleDebug — passed during implementation.
• iOS: Debug build for the arm64 iPhone 17 Pro simulator — passed during implementation; ./Testing/run-pure-swift-tests.sh — passed.
• Manual: installed on a HarmonyOS physical foldable and inspected home/welcome layouts; installed on Huawei_TripleFold and exercised live single/double/triple screen transitions.
• git diff upstream/main...HEAD --check — passed.

Reviewer Notes

Remote-control session data was exercised on HarmonyOS with a connected desktop. Remote workspace, peer-device mode, detached dispatch, and mixed-version end-to-end behavior were not exercised by this UI change. Dark-mode visual QA and Android/iOS device interaction parity remain unverified; semantic color checks passed.

Includes the earlier HarmonyOS MiniApp/interaction commits from this development branch. Latest upstream main is merged. Local HTML studies, build packages, signing material and IDE user state are excluded.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.