test: tighten coverage to 99.69% backend / 98.62% frontend

Started: 89.08% backend / 97.01% frontend lines.
Landed: 99.69% backend / 98.62% frontend.

Closed gaps targeted at logic gates, branches, and assumption boundaries
that real users hit. Each test exercises a use case the production code
actually serves; nothing here is line-padding.

Backend additions:
  - DeviceModelTest: pin landscape vs portrait dimension swap, plus the
    nativeWidth/Height "ignore orientation" contract the firmware relies on.
  - DeviceApiControllerTest: validation branches the PWA forms can't
    even produce (raw API misuse) — non-array wakeTimes, non-int entries,
    invalid rotation mode, invalid timezone, empty name, invalid orientation,
    other-user PATCH returns 404. Plus full /preview coverage: 404 for
    other-user / no-current / no-asset / missing-file / soft-deleted, and
    happy paths for landscape AND portrait (the rotateImage(90) branch).
  - ImageApiControllerTest: cropOrientation now exercised on both upload
    and reprocess paths.
  - TokenActionControllerTest: TK-01c covers the bad-device-id "continue"
    branch in submit.
  - RenderImageMessageHandlerTest: explicit portrait test pins the
    rotateImage(-90) branch and the 192,000-byte EPD-native bin shape.
  - SeedFakeDevicesCommandTest: 4 cases covering missing-user, fresh
    create, idempotent re-run, and --remove path. The dev seed command
    is load-bearing for the multi-frame UI; a silent break would surface
    a week later.
  - RerenderAssetsCommandTest: reset + dispatch path, no-assets path.

Frontend additions:
  - FrameCardTest: lastSync-only and nextSync-only rendering branches.
  - HomeView.test:
    * + Add time fallback path when all 9 default candidates are taken.
    * Multi-day "in Nd" nextSync formatting (offline / huge-interval case).
    * Medium-horizon (5h) nextSync formats as clock-time + day label.
    * visibilitychange triggers a silent re-fetch.
    * add-photo handler creates input + navigates to /upload after pick.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/test/components/FrameCard.test.ts

@@ -53,6 +53,29 @@ describe('FrameCard', () => {
     expect(wrapper.find('.frame-card__sync-line').exists()).toBe(false)
   })
 
+  // Cover the lastSync-without-nextSync branch: only the "synced X ago" span
+  // renders, no separator, no nextSync.
+  it('renders only lastSync when nextSync is absent', () => {
+    const wrapper = mount(FrameCard, {
+      props: { ...defaultProps, lastSync: '5m ago' },
+    })
+    const sync = wrapper.find('.frame-card__sync-line')
+    expect(sync.text()).toContain('synced 5m ago')
+    expect(sync.find('.frame-card__sync-sep').exists()).toBe(false)
+  })
+
+  // Inverse: nextSync without lastSync (a never-seen device that already has
+  // wakeTimes configured — the card should still preview the next slot).
+  it('renders only nextSync when lastSync is absent', () => {
+    const wrapper = mount(FrameCard, {
+      props: { ...defaultProps, nextSync: 'next sync ~6 AM tomorrow' },
+    })
+    const sync = wrapper.find('.frame-card__sync-line')
+    expect(sync.exists()).toBe(true)
+    expect(sync.text()).toContain('next sync ~6 AM tomorrow')
+    expect(sync.text()).not.toContain('synced')
+  })
+
   it('applies offline modifier class when status is offline', () => {
     const wrapper = mount(FrameCard, {
       props: { ...defaultProps, status: 'offline' },