Live wall: saved views in the URL hash, per-viewer memory, kiosk mode (#234)

- liveWall.ts: WallLink carries layers (short stable keys), z/lat/lon,
  base, tourMs, kiosk and an f.<name> filter pass-through for #235;
  parse/serialise stay pure and round-trip; old inc/cam/tour links parse.
- MapView: overlays/basemap/viewport come from initialLayers/initialBase/
  initialView (defaults unchanged); onViewStateChange reports layer, base
  and region-view changes (debounced). Initially-checked overlays now start
  "shown" (react-leaflet adds a checked overlay before the control can fire
  overlayadd). Closing an incident flies back to the pre-drill view (#137).
- wallPrefs.ts: per-browser last layers/base/view in localStorage, every
  access wrapped; precedence hash > remembered > defaults.
- LiveView: one effect mirrors wall + map state into the hash; hash edits
  remount the map with the new view; Copy view link; configurable tour.
- Kiosk (?kiosk=1 or #kiosk): no nav, fullscreen button (auto on first
  touch), Screen Wake Lock re-acquired on visibility, reconnect banner
  (offline / useCalls error) with backoff reload, 18-20 px type via a
  data-kiosk attribute and Tailwind arbitrary variants.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/lib/wallPrefs.ts

@@ -0,0 +1,51 @@
+/**
+ * Per-viewer memory of the live wall's map view (server-26#234): the last
+ * overlays, basemap and viewport this browser used. A convenience only —
+ * every access is wrapped, and a blocked/empty store (private window, cleared
+ * site data) simply yields {} so the wall falls back to its defaults.
+ *
+ * Precedence when the wall opens: URL hash > this store > defaults
+ * (resolveWallView below). Nothing here is shared with other viewers.
+ */
+import {
+  DEFAULT_BASE, DEFAULT_LAYERS, isBaseKey, normaliseLayers, parseViewport,
+  type WallView,
+} from "@/lib/liveWall";
+
+const KEY = "drb.wall.view.v1";
+
+export function loadWallPrefs(): WallView {
+  try {
+    const raw = window.localStorage.getItem(KEY);
+    if (!raw) return {};
+    const v: unknown = JSON.parse(raw);
+    if (!v || typeof v !== "object") return {};
+    const o = v as Record<string, unknown>;
+    const out: WallView = {};
+    if (Array.isArray(o.layers)) out.layers = normaliseLayers(o.layers.filter((x): x is string => typeof x === "string"));
+    if (typeof o.base === "string" && isBaseKey(o.base)) out.base = o.base;
+    const view = o.view && typeof o.view === "object" ? (o.view as Record<string, unknown>) : null;
+    const vp = view ? parseViewport(view.z, view.lat, view.lon) : undefined;
+    if (vp) out.view = vp;
+    return out;
+  } catch {
+    return {};
+  }
+}
+
+export function saveWallPrefs(v: WallView): void {
+  try {
+    window.localStorage.setItem(KEY, JSON.stringify({ layers: v.layers, base: v.base, view: v.view }));
+  } catch {
+    /* storage blocked or full — the URL hash still carries the view */
+  }
+}
+
+/** Field-by-field: hash wins, then what this browser remembers, then defaults. */
+export function resolveWallView(hash: WallView, stored: WallView): Required<Pick<WallView, "layers" | "base">> & Pick<WallView, "view"> {
+  return {
+    layers: hash.layers ?? stored.layers ?? DEFAULT_LAYERS,
+    base: hash.base ?? stored.base ?? DEFAULT_BASE,
+    view: hash.view ?? stored.view,
+  };
+}