feat(discover): seed showcase café coordinates so the map shows blinking lights

Showcase cafés (dev/staging only) now get Latitude/Longitude scattered around their real city (Tehran/Karaj) with a deterministic per-id offset, so the homepage Iran map renders a realistic cluster of blinking merchant lights. Backfills existing rows where coords are null. Production cafés get coordinates when owners set their location in dashboard Settings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Meezi.Infrastructure/Data/DiscoverShowcaseSeeder.cs

@@ -11,6 +11,28 @@ namespace Meezi.Infrastructure.Data;
 /// <summary>Seeds 30 Persian showcase cafés for public discover (development only).</summary>
 public static class DiscoverShowcaseSeeder
 {
+    // Approximate city centres. Each café is scattered around its city with a
+    // small deterministic offset (derived from its id) so the marketing map
+    // shows a realistic cluster of blinking lights instead of one stacked dot.
+    private static readonly Dictionary<string, (double Lat, double Lng, double Spread)> CityGeo = new()
+    {
+        ["تهران"] = (35.70, 51.39, 0.13),
+        ["کرج"] = (35.83, 50.99, 0.07),
+    };
+
+    private static (double Lat, double Lng) GeoFor(string id, string city)
+    {
+        var (lat, lng, spread) = CityGeo.TryGetValue(city, out var g) ? g : (35.70, 51.39, 0.13);
+        unchecked
+        {
+            var h = 17;
+            foreach (var ch in id) h = (h * 31) + ch;
+            var ox = (((h & 0xFFFF) / 65535.0) - 0.5) * 2 * spread;
+            var oy = ((((h >> 16) & 0xFFFF) / 65535.0) - 0.5) * 2 * spread;
+            return (Math.Round(lat + oy, 5), Math.Round(lng + ox, 5));
+        }
+    }
+
     private static readonly string[] ReviewAuthors = ["سارا", "علی", "مینا", "رضا", "نازنین"];
     private static readonly string[] ReviewComments =
     [
@@ -27,6 +49,7 @@ public static class DiscoverShowcaseSeeder
         foreach (var spec in DiscoverShowcaseCatalog.Cafes)
         {
             var cafe = await db.Cafes.FirstOrDefaultAsync(c => c.Id == spec.Id);
+            var (geoLat, geoLng) = GeoFor(spec.Id, spec.City);
             if (cafe is null)
             {
                 cafe = new Cafe
@@ -37,6 +60,8 @@ public static class DiscoverShowcaseSeeder
                     Slug = spec.Slug,
                     City = spec.City,
                     Address = spec.Address,
+                    Latitude = geoLat,
+                    Longitude = geoLng,
                     Description = spec.Description,
                     PlanTier = spec.PlanTier,
                     PreferredLanguage = "fa",
@@ -100,6 +125,12 @@ public static class DiscoverShowcaseSeeder
                     cafe.IsVerified = true;
                     changed = true;
                 }
+                if (cafe.Latitude is null || cafe.Longitude is null)
+                {
+                    cafe.Latitude = geoLat;
+                    cafe.Longitude = geoLng;
+                    changed = true;
+                }
                 if (changed)
                     await db.SaveChangesAsync();
             }