Update

API/ROLAC.API/Services/IOfferingSessionService.cs

@@ -21,4 +21,8 @@ public interface IOfferingSessionService
     Task SaveProofAsync(int id, Stream content, string fileName);
     Task<(Stream stream, string contentType)?> OpenProofAsync(int id);
     Task DeleteProofAsync(int id);
+
+    // Date-keyed variants for the anonymous mobile page (knows the date, not the id).
+    Task SaveProofForDateAsync(DateOnly date, Stream content, string fileName);
+    Task<(Stream stream, string contentType)?> OpenProofForDateAsync(DateOnly date);
 }

API/ROLAC.API/Services/OfferingSessionService.cs

@@ -183,6 +183,7 @@ public class OfferingSessionService : IOfferingSessionService
             Status = session.Status,
             SystemTotal = session.SystemTotal,
             LineCount = lines.Count,
+            HasProof = session.ProofPdfPath != null,
             Lines = await BuildLineDtosAsync(lines),
         };
     }
@@ -339,6 +340,39 @@ public class OfferingSessionService : IOfferingSessionService
         await _db.SaveChangesAsync();
     }
 
+    // ── Date-keyed proof (anonymous mobile page knows the date, not the id) ──
+
+    // Attach a proof PDF to the date's session, creating a Draft session if none
+    // exists yet (the volunteer may snap the count sheet before any line is keyed).
+    public async Task SaveProofForDateAsync(DateOnly date, Stream content, string fileName)
+    {
+        var session = await _db.OfferingSessions.FirstOrDefaultAsync(s => s.SessionDate == date);
+        if (session is null)
+        {
+            session = new OfferingSession { SessionDate = date, Status = "Draft" };
+            _db.OfferingSessions.Add(session);
+            try
+            {
+                await _db.SaveChangesAsync();
+            }
+            catch (DbUpdateException)
+            {
+                // Lost the create race — another phone inserted today's session first.
+                _db.ChangeTracker.Clear();
+                session = await _db.OfferingSessions.FirstAsync(s => s.SessionDate == date);
+            }
+        }
+        await SaveProofAsync(session.Id, content, fileName);
+    }
+
+    public async Task<(Stream stream, string contentType)?> OpenProofForDateAsync(DateOnly date)
+    {
+        var session = await _db.OfferingSessions.AsNoTracking()
+            .FirstOrDefaultAsync(s => s.SessionDate == date);
+        if (session is null) return null;
+        return await OpenProofAsync(session.Id);
+    }
+
     private static Giving MapLine(OfferingGivingLineRequest line, DateOnly sessionDate) => new()
     {
         MemberId            = line.IsAnonymous ? null : line.MemberId,