feat(giving): single-entry giving service with paging + lock guard

Adds GivingListItemDto, GivingDto, CreateGivingRequest, UpdateGivingRequest DTOs;
IGivingService interface; GivingService implementation with category/date filtering,
OfferingSession lock guard (Submitted/Reconciled), and DI registration in Program.cs.
Covered by 4 xUnit tests (TDD: red → green).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

API/ROLAC.API/DTOs/Giving/CreateGivingRequest.cs

@@ -0,0 +1,16 @@
+using System.ComponentModel.DataAnnotations;
+namespace ROLAC.API.DTOs.Giving;
+
+public class CreateGivingRequest
+{
+    public int?     MemberId            { get; set; }
+    [Required] public int GivingCategoryId { get; set; }
+    [Range(0.01, 9999999)] public decimal Amount { get; set; }
+    [Required, MaxLength(20)] public string PaymentMethod { get; set; } = "Cash";
+    [MaxLength(50)]  public string? CheckNumber         { get; set; }
+    [MaxLength(100)] public string? ZelleReferenceCode  { get; set; }
+    [MaxLength(100)] public string? PayPalTransactionId { get; set; }
+    public DateOnly GivingDate  { get; set; }
+    public bool     IsAnonymous { get; set; }
+    [MaxLength(500)] public string? Notes { get; set; }
+}

API/ROLAC.API/DTOs/Giving/GivingDto.cs

@@ -0,0 +1,18 @@
+namespace ROLAC.API.DTOs.Giving;
+
+public class GivingDto
+{
+    public int      Id                  { get; set; }
+    public int?     MemberId            { get; set; }
+    public string?  MemberName          { get; set; }
+    public int      GivingCategoryId    { get; set; }
+    public int?     OfferingSessionId   { get; set; }
+    public decimal  Amount              { get; set; }
+    public string   PaymentMethod       { get; set; } = "";
+    public string?  CheckNumber         { get; set; }
+    public string?  ZelleReferenceCode  { get; set; }
+    public string?  PayPalTransactionId { get; set; }
+    public DateOnly GivingDate          { get; set; }
+    public bool     IsAnonymous         { get; set; }
+    public string?  Notes               { get; set; }
+}

API/ROLAC.API/DTOs/Giving/GivingListItemDto.cs

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+namespace ROLAC.API.DTOs.Giving;
+
+public class GivingListItemDto
+{
+    public int      Id                { get; set; }
+    public int?     MemberId          { get; set; }
+    public string?  MemberName        { get; set; }
+    public int      GivingCategoryId  { get; set; }
+    public string   CategoryName      { get; set; } = "";
+    public decimal  Amount            { get; set; }
+    public string   PaymentMethod     { get; set; } = "";
+    public string   GivingDate        { get; set; } = ""; // ISO yyyy-MM-dd
+    public bool     IsAnonymous       { get; set; }
+    public int?     OfferingSessionId { get; set; }
+}

API/ROLAC.API/DTOs/Giving/UpdateGivingRequest.cs

@@ -0,0 +1,3 @@
+namespace ROLAC.API.DTOs.Giving;
+
+public class UpdateGivingRequest : CreateGivingRequest { }