INBOX-0: Gmail request inbox backend (MailKit) + Request entity + sync/triage endpoints

- Request entity (GmailMessageId unique, ThreadId, threading headers, From*, Subject, BodyText,
  ReceivedAt, Status enum-as-string New|InProgress|Assigned|Answered|Abandoned, AssignedContactId? FK,
  DraftReply?, AnsweredAt?). MailSettings singleton (GmailAddress, AppPassword ENCRYPTED via Data
  Protection, PollInterval, Folder, LastUid). Migration AddRequestsAndMailSettings.
- IGmailMailReader (mockable) + MailKit GmailMailReader (imap.gmail.com:993 SSL, envelope+X-GM-THRID
  +body). RequestSyncService: dedup on Message-Id, track LastUid. MailKit 4.17.0.
- Endpoints: POST /api/requests/sync, GET /api/requests (Gridify, filter status), GET /api/requests/{id},
  PUT triage (status+assignedContactId), GET/PUT /api/mail-settings (App Password never returned).
- Tests (in-memory DB + canned reader): sync dedup/idempotency/config-guard, HTTP sync->triage->assign,
  mail-settings secrecy. + gitignore the runtime photo-storage/ dir (god housekeeping).

GerbilManagerWebAPI/Dtos/InboxDtos.cs

@@ -0,0 +1,38 @@
+using GerbilManagerWebAPI.Models;
+
+namespace GerbilManagerWebAPI.Dtos
+{
+    public record RequestDto(
+        Guid Id,
+        string GmailMessageId,
+        string? ThreadId,
+        string FromAddress,
+        string? FromName,
+        string? Subject,
+        string? BodyText,
+        DateTimeOffset ReceivedAt,
+        RequestStatus Status,
+        Guid? AssignedContactId,
+        string? DraftReply,
+        DateTimeOffset? AnsweredAt);
+
+    /// <summary>Triage update: change status and/or assign a contact.</summary>
+    public record RequestTriageInput(RequestStatus? Status, Guid? AssignedContactId);
+
+    /// <summary>Mail settings read shape — the App Password is NEVER returned (only HasAppPassword).</summary>
+    public record MailSettingsDto(
+        string? GmailAddress,
+        int PollIntervalMinutes,
+        string Folder,
+        bool BackgroundPollEnabled,
+        bool HasAppPassword);
+
+    /// <summary>Mail settings write shape. AppPassword is write-only; null/omitted leaves it unchanged,
+    /// empty string clears it.</summary>
+    public record MailSettingsInput(
+        string? GmailAddress,
+        string? AppPassword,
+        int? PollIntervalMinutes,
+        string? Folder,
+        bool? BackgroundPollEnabled);
+}