refactor(phase0): devices, manual apps, focus editor and changelog become shells

[adamXbot]

What

Batch 2 of Rust-core Phase 0 — 11 of 35 pages converted. These four shared exactly two server concerns, and both now resolve through the API.

Flag gates. resolveFlagFromDb(key) !== "on" → notFound() becomes RequireFlagGate, reading the resolved value from GET /api/feature-flags (flags[].currentValue — the same resolver output, not a re-implementation). Two details worth review attention:

• It fails closed: a failed flag read renders the 404, not the page. These gates hide surfaces that shouldn't exist for an install, so "couldn't tell" must not fall open.
• notFound() is thrown during render from state, not from the effect — the only way it works in a client component.

Initial data. Every list already had an exact API twin, so no new endpoints were needed:

Page	Source	Note
settings/devices	/api/devices	already includes appCount; DevicesView already fetched it in refresh()
dashboard/manual-apps	/api/manual-apps	already returned the exact { apps, sources } pair the page assembled by hand
settings/focus	/api/focus	already returned all six fields; new FocusEditLoader maps them
/changelog	/api/apps	filter dropdown

FocusEditLoader holds the form back until the fetch lands — FocusEditForm stages edits from its initial props, so mounting with placeholders then swapping would either be ignored or clobber user input.

The initialX props stay optional on the three views so their Storybook stories keep seeding fixtures (there the mount fetch fails and the seeded state stands).

Verification

• By hand, where no e2e covers it: both gated pages render with their data through the gate; the manual-app form still defaults to Safari web app (sources[0] — unchanged, since both create paths reset from live sources and the deep-link path's fallback was already web_clip); flipping flag.page.manual_apps off renders the real 404 page.
• Gate: tsc clean · biome clean · unit 462 pass / 0 fail · full Playwright 46 passed · visual net 13/13 pixel-identical against pre-conversion baselines captured via stash.

Next

Batch 3 takes the pages needing small new read endpoints (stats, privacy map, shortlist, review-recommendations), then the big three (dashboard, app detail, apps grid), with the layout/CSP batch last and coming to you for sign-off.

🤖 Generated with Claude Code

[adamXbot]

Superseded by #199, which consolidates Phase 0 batches 2–6 into a single PR (32 of 35 pages). This branch's commits are all contained in that one — closing to avoid a partial merge landing ahead of it.