feat(map): backfill café coordinates from city on startup (prod-safe)

Real cafés without a map pin now get approximate coordinates at their city centre (with a deterministic per-café offset) on every boot, in all environments, so the public Iran map lights up with merchant dots. Only fills rows where Latitude/Longitude is null and the city is recognised (20 major Iranian cities); never overwrites an owner-set pin. Owners can drop an exact pin from Settings.

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

src/Meezi.Infrastructure/Data/PlatformDataSeeder.cs

@@ -29,6 +29,10 @@ public static class PlatformDataSeeder
         // fresh deploy. Idempotent. Phone is overridable via "Seed:SystemAdminPhone".
         await EnsureOwnerAdminAsync(db, config, logger);
 
+        // Production-safe: give cafés without a map pin an approximate location
+        // from their city, so the public map lights up. Idempotent (fills nulls).
+        await BackfillCafeLocationsAsync(db, logger);
+
         if (!env.IsDevelopment())
         {
             // Production: also ensure integration settings (Kavenegar enabled/template,
@@ -45,6 +49,79 @@ public static class PlatformDataSeeder
         await EnsureIntegrationSettingsAsync(db, logger);
     }
 
+    // Approximate centres for the major Iranian cities cafés sign up from.
+    private static readonly Dictionary<string, (double Lat, double Lng)> CityCentres = new(StringComparer.Ordinal)
+    {
+        ["تهران"] = (35.70, 51.39),
+        ["کرج"] = (35.84, 50.99),
+        ["مشهد"] = (36.30, 59.61),
+        ["اصفهان"] = (32.66, 51.67),
+        ["شیراز"] = (29.59, 52.53),
+        ["تبریز"] = (38.08, 46.29),
+        ["قم"] = (34.64, 50.88),
+        ["اهواز"] = (31.32, 48.67),
+        ["کرمانشاه"] = (34.31, 47.07),
+        ["رشت"] = (37.28, 49.58),
+        ["ارومیه"] = (37.55, 45.07),
+        ["همدان"] = (34.80, 48.52),
+        ["یزد"] = (31.90, 54.37),
+        ["اراک"] = (34.09, 49.69),
+        ["کرمان"] = (30.28, 57.08),
+        ["بندرعباس"] = (27.18, 56.27),
+        ["قزوین"] = (36.28, 50.00),
+        ["ساری"] = (36.57, 53.06),
+        ["گرگان"] = (36.84, 54.44),
+        ["زنجان"] = (36.68, 48.49),
+        ["کیش"] = (26.56, 53.98),
+    };
+
+    /// <summary>
+    /// Gives cafés that have no map pin an approximate location at their city
+    /// centre (plus a small deterministic per-café offset so multiple cafés in
+    /// one city don't stack on a single point). Only fills rows where Latitude or
+    /// Longitude is null and the city is recognised; owners can drop an exact pin
+    /// later from Settings. Idempotent — never overwrites an existing pin.
+    /// </summary>
+    private static async Task BackfillCafeLocationsAsync(AppDbContext db, ILogger logger)
+    {
+        var cafes = await db.Cafes
+            .Where(c => c.DeletedAt == null
+                && (c.Latitude == null || c.Longitude == null)
+                && c.City != null)
+            .ToListAsync();
+        if (cafes.Count == 0) return;
+
+        var updated = 0;
+        foreach (var cafe in cafes)
+        {
+            var city = cafe.City!.Trim();
+            if (!CityCentres.TryGetValue(city, out var centre)) continue;
+            var (lat, lng) = ScatterAround(cafe.Id, centre.Lat, centre.Lng, 0.05);
+            cafe.Latitude = lat;
+            cafe.Longitude = lng;
+            updated++;
+        }
+
+        if (updated > 0)
+        {
+            await db.SaveChangesAsync();
+            logger.LogInformation(
+                "Cafe location backfill: set approximate coordinates for {Count} café(s) from city centre", updated);
+        }
+    }
+
+    private static (double Lat, double Lng) ScatterAround(string id, double lat, double lng, double spread)
+    {
+        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));
+        }
+    }
+
     /// <summary>
     /// Ensures the platform owner's system-admin account exists in EVERY environment
     /// (including production), so the admin panel is reachable on a fresh deploy.