Add zip-to-zip distance calculation for vendor dispatch

- ZipCodeDistance helper with Haversine formula on 33K US zip code centroids
- Loaded as singleton from wwwroot/zipcodes.csv on startup
- Vendor Dropdown endpoint accepts siteZip, returns address and distanceMiles
- Vendors sorted by distance when siteZip provided
- Include locationZip in GetWorkorderById response

Api.SeaHavenIndustries/Controllers/VendorController.cs

@@ -13,10 +13,12 @@ namespace Api.SeaHavenIndustries.Controllers
     public class VendorController : Controller
     {
         private readonly ApplicationDbContext _db;
+        private readonly Helper.ZipCodeDistance _zipDistance;
 
-        public VendorController(ApplicationDbContext db)
+        public VendorController(ApplicationDbContext db, Helper.ZipCodeDistance zipDistance)
         {
             _db = db;
+            _zipDistance = zipDistance;
         }
 
         [HttpGet("GetVendorList")]
@@ -155,22 +157,51 @@ namespace Api.SeaHavenIndustries.Controllers
         }
 
         [HttpGet("Dropdown")]
-        public async Task<IActionResult> GetDropdown([FromQuery] string? trade = null)
+        public async Task<IActionResult> GetDropdown([FromQuery] string? trade = null, [FromQuery] string? siteZip = null)
         {
             var query = _db.Vendors.Where(v => v.IsActive);
 
             var vendors = await query.OrderBy(v => v.CompanyName)
-                .Select(v => new { v.Id, v.CompanyName, v.TradeSpecialties })
+                .Select(v => new
+                {
+                    v.Id,
+                    v.CompanyName,
+                    v.TradeSpecialties,
+                    v.Address,
+                    v.City,
+                    v.State,
+                    v.Zip
+                })
                 .ToListAsync();
 
+            var result = vendors.Select(v =>
+            {
+                var distance = _zipDistance.GetDistanceMiles(siteZip, v.Zip);
+                var addr = new[] { v.Address, v.City, v.State, v.Zip }
+                    .Where(s => !string.IsNullOrWhiteSpace(s));
+                return new
+                {
+                    v.Id,
+                    v.CompanyName,
+                    v.TradeSpecialties,
+                    address = string.Join(", ", addr),
+                    distanceMiles = distance.HasValue ? Math.Round(distance.Value, 1) : (double?)null
+                };
+            }).ToList();
+
             if (!string.IsNullOrWhiteSpace(trade))
             {
-                var tradeMatched = vendors.Where(v => (v.TradeSpecialties ?? "").Contains(trade)).ToList();
-                var rest = vendors.Where(v => !(v.TradeSpecialties ?? "").Contains(trade)).ToList();
-                vendors = tradeMatched.Concat(rest).ToList();
+                var tradeMatched = result.Where(v => (v.TradeSpecialties ?? "").Contains(trade)).ToList();
+                var rest = result.Where(v => !(v.TradeSpecialties ?? "").Contains(trade)).ToList();
+                result = tradeMatched.Concat(rest).ToList();
             }
 
-            return Ok(vendors);
+            if (!string.IsNullOrWhiteSpace(siteZip))
+            {
+                result = result.OrderBy(v => v.distanceMiles ?? 99999).ToList();
+            }
+
+            return Ok(result);
         }
     }
 }

Api.SeaHavenIndustries/Controllers/WorkOrderController.cs

@@ -610,6 +610,7 @@ namespace Api.SeaHavenIndustries.Controllers
                 assignee = s.AssignToUser != null ? s.AssignToUser.FirstName : "",
                 location = s.Locations != null ? s.Locations.Name : "",
                 locationId = s.LocationId,
+                locationZip = s.Locations != null ? s.Locations.ZipCode : "",
                 priority = s.Priority,
                 s.Problem,
                 s.Trade,

Api.SeaHavenIndustries/Helper/ZipCodeDistance.cs

@@ -0,0 +1,48 @@
+namespace Api.SeaHavenIndustries.Helper
+{
+    public class ZipCodeDistance
+    {
+        private readonly Dictionary<string, (double lat, double lng)> _coords = new();
+        private bool _loaded;
+
+        public void Load(string csvPath)
+        {
+            if (_loaded) return;
+            foreach (var line in File.ReadLines(csvPath).Skip(1))
+            {
+                var parts = line.Split(',');
+                if (parts.Length >= 3
+                    && double.TryParse(parts[1].Trim(), out var lat)
+                    && double.TryParse(parts[2].Trim(), out var lng))
+                {
+                    _coords[parts[0].Trim().PadLeft(5, '0')] = (lat, lng);
+                }
+            }
+            _loaded = true;
+        }
+
+        public double? GetDistanceMiles(string? zip1, string? zip2)
+        {
+            if (string.IsNullOrWhiteSpace(zip1) || string.IsNullOrWhiteSpace(zip2)) return null;
+            var z1 = zip1.Trim().PadLeft(5, '0');
+            var z2 = zip2.Trim().PadLeft(5, '0');
+            if (z1.Length > 5) z1 = z1.Substring(0, 5);
+            if (z2.Length > 5) z2 = z2.Substring(0, 5);
+            if (!_coords.TryGetValue(z1, out var c1) || !_coords.TryGetValue(z2, out var c2)) return null;
+            return Haversine(c1.lat, c1.lng, c2.lat, c2.lng);
+        }
+
+        private static double Haversine(double lat1, double lon1, double lat2, double lon2)
+        {
+            const double R = 3958.8;
+            var dLat = ToRad(lat2 - lat1);
+            var dLon = ToRad(lon2 - lon1);
+            var a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2) +
+                    Math.Cos(ToRad(lat1)) * Math.Cos(ToRad(lat2)) *
+                    Math.Sin(dLon / 2) * Math.Sin(dLon / 2);
+            return R * 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
+        }
+
+        private static double ToRad(double deg) => deg * Math.PI / 180.0;
+    }
+}

Api.SeaHavenIndustries/Program.cs

@@ -32,6 +32,14 @@ builder.Services.AddResponseCompression(opts =>
 builder.Services.AddCors(option =>
 option.AddDefaultPolicy(builder => builder.AllowAnyOrigin().AllowAnyHeader().AllowAnyMethod()));
 builder.Services.AddScoped<SendMessage>();
+builder.Services.AddSingleton<Api.SeaHavenIndustries.Helper.ZipCodeDistance>(sp =>
+{
+    var zipService = new Api.SeaHavenIndustries.Helper.ZipCodeDistance();
+    var env = sp.GetRequiredService<IWebHostEnvironment>();
+    var csvPath = Path.Combine(env.WebRootPath, "zipcodes.csv");
+    if (File.Exists(csvPath)) zipService.Load(csvPath);
+    return zipService;
+});
 builder.Services.AddAuthentication(options =>
 {
     options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;