feat(hunt): track walking distance via GPS, show live locations on map

Add foreground-only GPS distance tracking for hunts

app/composables/useTeamColors.ts

@@ -0,0 +1,65 @@
+/**
+ * Client-only team color assignment for the live map.
+ *
+ * A fixed 20-color high-contrast palette is shuffled once per page-load and
+ * assigned to teams by their stable order (the order returned by the map
+ * endpoint). Colors are team-shared but NOT persisted, so a refresh may
+ * reassign them. Every member of a team resolves to the same color.
+ */
+
+const PALETTE = [
+  '#e6194b',
+  '#3cb44b',
+  '#4363d8',
+  '#f58231',
+  '#911eb4',
+  '#46f0f0',
+  '#f032e6',
+  '#bcf60c',
+  '#fabebe',
+  '#008080',
+  '#e6beff',
+  '#9a6324',
+  '#fffac8',
+  '#800000',
+  '#aaffc3',
+  '#808000',
+  '#ffd8b1',
+  '#000075',
+  '#808080',
+  '#ff4d00'
+] as const;
+
+function shuffled<T>(input: readonly T[]): T[] {
+  const arr = [...input];
+  for (let i = arr.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));
+    [arr[i], arr[j]] = [arr[j]!, arr[i]!];
+  }
+  return arr;
+}
+
+/** Darken a hex color by a factor (0..1) for trail lines. */
+export function darken(hex: string, factor = 0.75): string {
+  const n = parseInt(hex.slice(1), 16);
+  const r = Math.round(((n >> 16) & 255) * factor);
+  const g = Math.round(((n >> 8) & 255) * factor);
+  const b = Math.round((n & 255) * factor);
+  return `#${((1 << 24) | (r << 16) | (g << 8) | b).toString(16).slice(1)}`;
+}
+
+export function useTeamColors() {
+  // Shuffled once per composable instance (i.e. per page-load).
+  const colors = shuffled(PALETTE);
+
+  /** Build a teamId -> color map from an ordered list of team ids. */
+  function assign(orderedTeamIds: number[]): Map<number, string> {
+    const map = new Map<number, string>();
+    orderedTeamIds.forEach((id, i) => {
+      map.set(id, colors[i % colors.length]!);
+    });
+    return map;
+  }
+
+  return { assign, colors, darken };
+}