Make stations view work without GPS + add header station search overlay

[ciotlosm]

Summary

The Stations view (/) currently auto-triggers the browser's geolocation
prompt on first visit via onMount(() => locationStore.start()) in
src/routes/+page.svelte. This
issue makes GPS strictly opt-in, gives a useful default experience
without it, and adds a station search overlay (reusable from any view via
the header) so the rider can always find a stop.

What's already there (no work needed)

• getStationBoardsNear / getStopsNear worker queries in
  src/lib/workers/gtfs/queries/stops.ts
  and
  stationBoards.ts.
• A hardcoded Cluj city-center fallback in +page.svelte
  (FALLBACK_LAT / FALLBACK_LON) — gets deleted in §1.
• Feed.center: { lat, lon } on
  src/lib/data/feeds.ts —
  published by neary-gtfs and
  derived from the feed's bbox in make-sqlite.js. This is the
  distance anchor for the GPS-off fallback.
• userPrefs persistence pattern in
  src/lib/stores/userPrefs.svelte.ts
  for opt-in / dismiss state.
• The header (src/lib/ui/Header.svelte) already has the GPS dot — the
  search icon lives next to it.

What changes

1. Make GPS strictly opt-in

• Remove onMount(() => locationStore.start()) from
  src/routes/+page.svelte. The browser must not prompt on first
  visit.
• Delete the hardcoded FALLBACK_LAT / FALLBACK_LON constants. The
  fallback anchor becomes
  feedsStore.byId(feedsStore.boundFeedId)?.center (or a sensible default
  if the feed's center is missing — file a follow-up if that ever
  happens).
• The gpsState derivation in +page.svelte gains a fourth value:
  • 'not-opted-in' — user has never tapped Enable.
  • 'pending' — opted in, waiting for first fix.
  • 'available' / 'unavailable' — unchanged.
    The current 'pending' covers both "opted in, waiting" and "never
    asked"; the new value separates them so the banner can target the
    opt-in case.

2. In-page "Enable location" banner with transparency copy

When gpsState === 'not-opted-in', render a single horizontal banner at
the top of the Stations view (replacing today's "No GPS" indicator). Copy:

📍 See stops near you — Neary uses your location to sort nearby
stations and put real-time arrivals closer to you first. We never store
it, never send it to a server, and never track you in the background.
[Enable location] [Not now]

• Enable location → calls locationStore.start(), which triggers the
  browser's native permission dialog.
• Not now → dismisses the banner; persists in userPrefs via a new
  gpsPromptDismissedAt: number | null (timestamp). Cleared (set back to
  null) the moment the user opts in.
• When gpsState === 'unavailable' (permission denied), the banner copy
  changes to: "Location is off in your browser settings. Open Settings →
  Site permissions → Location to allow it." The Enable button is hidden.
• When gpsState === 'available', the banner is gone entirely.

3. Header GPS dot gets an off state

FreshState in src/lib/stores/locationStore.svelte.ts becomes:

type FreshState = 'off' | 'idle' | 'ok' | 'stale' | 'error';

• 'off' — user has never opted in. Tooltip: "GPS off — tap to enable."
  Tapping the header dot also calls locationStore.start() (second
  entry point next to the in-page banner).
• 'idle' — opted in, waiting for first fix. Existing behavior.
• 'ok' / 'stale' / 'error' — unchanged.

The existing gpsState derivation in +page.svelte and the header dot
(src/lib/ui/Header.svelte) both consume the new state.

4. Header search icon + dimmed-overlay search

• New magnifying-glass icon button in the header (Header.svelte),
  next to the GPS dot. Header is global, so the icon is visible on
  every view (Stations, Favorites, Settings, future Planner).
• Tap → opens a full-screen overlay with:
  • A dimmed backdrop behind it (a semi-transparent layer that
    dismisses the overlay on tap-outside).
  • A centered search box in the middle of the screen. On mobile,
    this is the area that gets pushed up by the soft keyboard, so the
    search stays usable without scrolling.
  • A scrollable list of matching stations under the input.
  • A small "Cancel" affordance top-right of the overlay to close.
• Input behavior:
  • Empty input → debounce 150ms, then show the 25 nearest stations
    to the current anchor (GPS position if available, else
    feedsStore.activeFeed.center).
  • Non-empty input → debounce 150ms, then call the new worker query
    (§5). Show results sorted by distance from the anchor ascending.
  • Tapping a result → goto('/station/[id]') and close the overlay.
• No URL state for now — the search lives in component state. If we
  want shareable searches later, add /?q=... then.
• The header's search icon is always visible — the only requirement is
  that a feed is selected. If userPrefs.feedId == null, hide the icon
  (no stations to search).

5. New worker query: searchStops

Add to src/lib/workers/gtfs/queries/stops.ts:

searchStops(
  db: Database,
  text: string,         // '' → nearest-only, no name filter
  anchorLat: number,
  anchorLon: number,
  limit: number,        // default 25
): StopWithDistance[]

Implementation:

• text === '' → just call the existing getStopsNear(...) and return
  its result. Zero new code for the empty-input case.
• text !== '' → SQL WHERE stop_name LIKE ? COLLATE NOCASE with the
  same bounding-box prefilter as getStopsNear (uses the lat/lon index),
  then Haversine distance in JS, then sort + slice.
• Substring match (%${text}%). Diacritic-insensitive: normalize both
  the input and stop_name with String.prototype.normalize('NFD') and
  strip combining marks, so "piata" matches "Piața". Cheap, no extra
  index.
• Keep the EXISTS (SELECT 1 FROM stop_times ...) filter that
  getStopsNear already has, so legacy / terminus-pad stops never
  surface in the search results.

Surface in the repo (src/lib/data/gtfs/repo.ts):

searchStops(
  text: string,
  anchorLat: number,
  anchorLon: number,
  limit?: number,
): Promise<StopWithDistance[]>

6. (Forward-looking) "Show on map" in search results

Deferred — blocked on #104 (Planner view). When that ships, each
search-result row gets a small map-pin icon that navigates to the
planner's origin-pick surface pre-filled with the stop id.

Tracked as a follow-up comment on this issue, not a separate issue, so
the dependency stays visible.

Acceptance criteria

• First visit, no feed selected → existing empty state.
• First visit, feed selected, GPS off → fallback board renders using
  the feed's center; the opt-in banner is visible.
• Tap Enable location → browser permission dialog appears. Grant
  → board re-queries with GPS position. Deny → banner switches to
  "permission denied" copy.
• Tap Not now → banner disappears, persists across reloads
  (userPrefs.gpsPromptDismissedAt is set), reappears after a manual
  reset (out of scope to expose the reset; just document it).
• Header GPS dot shows 'off' (grey, tooltip "GPS off — tap to
  enable") when not opted in. Tapping it opts in.
• Search icon is visible in the header on every view except
  /settings and the empty state. Tapping it opens the overlay
  with a dimmed backdrop and a centered search input.
• Overlay empty input → 25 nearest stations to the current anchor
  (GPS or feed center), sorted ascending by distance.
• Type aeroport → list filters to matching stops, sorted by
  distance from the anchor. "piata" matches "Piața".
• Tap a result → navigates to /station/[id], overlay closes.
• Mobile: open the search overlay, focus the input → the keyboard
  pushes the input up; the input stays visible and the result list
  shrinks but remains scrollable. Tap the dimmed backdrop → overlay
  dismisses.
• npm run check && npm test && npm run build all pass.
• No new console.log in production code.

Out of scope (separate issues if needed)

• The Feed type's center is assumed to always be present. If a feed
  ever ships without one, file a follow-up for a per-feed override.
  Likewise, a separate "downtown" coordinate distinct from the bbox
  centroid would be a new optional field on the neary-gtfs feeds.json
  schema, not an app-only change.
• Reverse geocoding — turning the fallback position into a human-readable
  place name. The feed name in the header is enough for now.
• Persisting the search query across sessions.
• Per-station "favorites"-based empty-state behavior — unchanged.

References

• Planner view: map-first itineraries (build on header search overlay) #104 — Planner view (the future "show on map" target).
• neary-gtfs feeds.json schema:
  schemas/feeds.schema.json.
• src/routes/+page.svelte
• src/lib/stores/locationStore.svelte.ts
• src/lib/stores/userPrefs.svelte.ts
• src/lib/ui/Header.svelte
• src/lib/workers/gtfs/queries/stops.ts
• src/lib/workers/gtfs/queries/stationBoards.ts
• src/lib/data/feeds.ts