feat: doctor reply + diagnosis + tracking code per health request

Backend:
- HealthRequest model: TrackingCode (DR-XXXXXX), Diagnosis,
  DoctorReply, RepliedAt fields
- Runtime migration: ALTER TABLE adds 4 new columns to existing DB
- POST /api/health-request: auto-generates tracking code, returns it
- PUT /api/health-requests/{id}/reply: doctor sets diagnosis + reply
- GET /api/health-request/track/{code}: public lookup by tracking code
- GET /api/health-requests?phone=: filter history by phone number

Admin panel:
- Request table shows tracking code column (gold badge)
- Detail modal (680px): tracking code header, patient info, full message
- Previous doctor reply shown in green box if exists
- Reply form: diagnosis input + textarea for doctor message
- History panel: all requests from same phone, click to switch
- 'پاسخ / مشاهده' button opens reply modal directly

Frontend:
- After form submit: shows tracking code in green box to user
  (format: DR-XXXXXX, stays visible 8 seconds)
- Box auto-hides and form resets after timeout

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

DrSousan.Api/Models/Models.cs

@@ -171,17 +171,23 @@ public class PatientVisit
 public class HealthRequest
 {
     public int Id { get; set; }
-    [MaxLength(150)] public string FullName    { get; set; } = "";
-    [MaxLength(20)]  public string PhoneNumber { get; set; } = "";
-    [MaxLength(200)] public string Email       { get; set; } = "";
-    public string Message  { get; set; } = "";
-    [MaxLength(20)]  public string Category    { get; set; } = "beauty"; // beauty | health
-    public bool     IsHandled { get; set; } = false;
-    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
+    [MaxLength(20)]  public string TrackingCode { get; set; } = "";   // e.g. DR-A3F7K2
+    [MaxLength(150)] public string FullName     { get; set; } = "";
+    [MaxLength(20)]  public string PhoneNumber  { get; set; } = "";
+    [MaxLength(200)] public string Email        { get; set; } = "";
+    public string Message   { get; set; } = "";
+    [MaxLength(20)]  public string Category     { get; set; } = "beauty"; // beauty | health
+    public bool     IsHandled  { get; set; } = false;
+    // Doctor response
+    public string Diagnosis   { get; set; } = "";   // پزشک: تشخیص
+    public string DoctorReply { get; set; } = "";   // پزشک: پاسخ/توضیح
+    public DateTime? RepliedAt { get; set; }
+    public DateTime CreatedAt  { get; set; } = DateTime.UtcNow;
 }
 
 // ─── DTOs ─────────────────────────────────────────────────────────────────────
 public record LoginRequest(string Username, string Password);
+public record DoctorReplyDto(string? Diagnosis, string? DoctorReply);
 public record ChangePasswordRequest(string CurrentPassword, string NewPassword);
 public record SettingDto(string Key, string Value);
 public record BulkSettingsDto(Dictionary<string, string> Settings);