feat(WhereUI): add a subtle personalized Locations background

[kyleve]

Summary

Add a stationary monochrome region pattern behind the Locations tab, layered over faint full-view rosette rings. Alternate rows shift by half a cell. A 54-point preferred cell pitch keeps the repeat compact, with compensated artwork extent to preserve the region size. The print uses flat, faint strokes without shadows; slender regions receive a bounded size adjustment to balance the marks.

The pattern includes visited geographic regions in the selected year, including manual entries and Elsewhere. The catch-all Other entry is omitted from the print, so the background has no globe icons or empty placeholder cells. It uses catalog order so ranking changes do not rearrange it. Repeated cells extend beyond all four edges, and every region retains a fully visible copy.

Why

Extend the personalized print on the region cards into a quieter screen background while preserving a continuous staggered repeat.

Review focus

• Appearance lives in dedicated stylesheet tokens. Region paths come from the existing injected cache; full-view rosettes use the existing shared renderer.
• Layout keeps square cells with a half-cell horizontal offset on alternating rows and overscan at every edge.
• Obsolete artwork is hidden when membership changes. Empty, initial-loading, and failed states retain only full-view rosettes. Reduce Transparency hides all decorative ink.
• Screen snapshots allow one second for native glass and artwork settling. The loaded fixture warms its outline cache before capture, including accessibility preparation.
• No persistence, public API, or dependency changes.

Testing

• Focused layout and stylesheet tests passed, covering half-cell row offsets, overscan, full region coverage, and empty history.
• 52 reviewed captures across LocationsBackground, LocationsView, MainTabs, and RootView, including light/dark, iPad, accessibility sizes, and Reduce Transparency.
• Architecture validation and 15 rule tests passed.
• Refreshed the MainTabs welcome references for the full-view rosettes; CI exposed a stale dark-mode reference. Compared the affected screen suites after merging the current main branch.
• SwiftFormat, SF Symbol lint, and diff whitespace checks passed.
• Live scrolling and year-switch gestures were not manually exercised; membership changes and stale-load suppression have unit coverage.

./test --no-generate \
  --only WhereUITests/LocationsBackgroundLayoutTests \
  --only WhereUITests/WhereStylesheetTests \
  --only WhereUISnapshotTests/LocationsBackgroundSnapshotTests \
  --only WhereUISnapshotTests/LocationsViewSnapshotTests \
  --only WhereUISnapshotTests/MainTabsSnapshotTests \
  --only WhereUISnapshotTests/RootViewSnapshotTests --record all
./test --no-generate --no-build \
  --only WhereUISnapshotTests/LocationsBackgroundSnapshotTests \
  --only WhereUISnapshotTests/LocationsViewSnapshotTests \
  --only WhereUISnapshotTests/MainTabsSnapshotTests \
  --only WhereUISnapshotTests/RootViewSnapshotTests --review

The recording run reports intentional recording failures; the final comparison verifies the reviewed references.

[kyleve]

Maybe not for this PR, but I think we have this duplicated in a few spots, maybe a good candidate for a shared modifier of some sort?

[kyleve]

Posted by an AI agent on @kyleve's behalf.

Extracted this in #325 (commit b9b63d4). The Locations background, Elsewhere card, region cards, welcome card, and forecast panel now share regionArtworkTask plus RegionArtworkModel. The shared lifecycle handles cache injection, cancellation, and stale results, while the region card retains compatible outlines during point refreshes. Fifteen focused tests and six existing snapshot suites passed without reference changes. Since #324 has merged, the follow-up targets main.