refactor(settings): consolidate per-page skeletons and extract page helpers

[Astro-Han]

Summary

Three small, behavior-preserving refactors consolidating duplicated and inlined code in the settings surface. No user-visible change; rendered DOM is equivalent.

• Loading skeletons: permission-center, health-center, and about each hand-wrote a near-identical maka-skeleton-stack with aria-busy/aria-label. Extracted SettingsSkeletonStack (label + optional lines, snapshot preset as default) and routed the three pages through it. SettingsSkeleton (the settings-surface shell) is untouched.
• Memory page helpers: the 11 React-free label/format/filter helpers at the tail of memory-settings-page.tsx (~115 lines) moved to memory-settings-labels.ts and imported back.
• WeChat login flow: BotWeChatFields, WeChatScanLoginModal, and WechatQrLoginModal (~370 lines of self-contained scan/QR login) moved from bot-chat-settings-page.tsx to bot-wechat-login.tsx; dropped the now-unused X / DialogRoot / DialogContent / WechatBridgeQrCodeResult imports from the host page.

Why

The three largest settings pages each carried a chunk of code that was either duplicated across pages or self-contained enough to live on its own. This trims bot-chat-settings-page.tsx (1323 → 937) and memory-settings-page.tsx (1213 → 1096) and removes the per-page skeleton copy-paste. app-shell.tsx (1687) and chat-view.tsx (1744) were intentionally left alone — both already have extensive sibling modules and are large because they are coordination hubs, not because they are under-factored.

Scope

Changed:

• settings-skeleton.tsx — added SettingsSkeletonStack
• permission-center-page.tsx, health-center-page.tsx, about-settings-page.tsx — route through SettingsSkeletonStack
• memory-settings-labels.ts (new) + memory-settings-page.tsx
• bot-wechat-login.tsx (new) + bot-chat-settings-page.tsx
• settings-contract-source-helpers.ts — registered the two new files in SETTINGS_SOURCE_REPO_PATHS
• settings-app-info-contract.test.ts — synced one assertion literal

Not included: app-shell.tsx, chat-view.tsx, ProvidersPanel loading state (different pattern, not a maka-skeleton-stack).

Verification

• npm run build:main (tsc typecheck) — pass
• npm run build:renderer (vite) — pass
• node --test "dist/main/**/*.test.js" — 2262 pass, 0 fail
• npm run test:checks (console / a11y / copy) — pass

User-facing impact

None. Pure refactor.

Reviewer notes

• The settings contract tests are source-text based: they regex over a concatenated mirror of the settings source files. The two new files are registered in SETTINGS_SOURCE_REPO_PATHS right after their host pages, so the concatenated mirror contains the same code and the blockBetween boundaries still resolve — some now span two files (e.g. MemoryEntryList … filterLocalMemoryEntries), which the non-greedy match handles fine.
• One assertion in settings-app-info-contract matched the literal aria-label="正在加载关于页" source; synced to label="正在加载关于页" to follow the new component prop. Same intent: the skeleton carries that accessible label while loading.
• Skeleton DOM equivalence is preserved per page: same line count, widths, and data-size values render to the same markup.
• Three commits, one per concern (skeleton / memory / WeChat), each independently revertable.

Checklist

• Scope matches the PR title and excludes unrelated changes
• Verification lists commands/results
• User-facing impact: none
• Risk: source-text contract tests called out above
• UI changes: none (refactor only, no screenshot needed)