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/Inbox/MailContracts.cs

@@ -0,0 +1,29 @@
+namespace GerbilManagerWebAPI.Inbox
+{
+    /// <summary>Connection params for an IMAP fetch (decrypted password — never persisted/logged).</summary>
+    public sealed record MailConnection(string GmailAddress, string AppPassword, string Folder);
+
+    /// <summary>A fetched email reduced to what the Request entity needs.</summary>
+    public sealed record MailSummary(
+        string MessageId,
+        string? ThreadId,
+        string? InReplyTo,
+        string? References,
+        string FromAddress,
+        string? FromName,
+        string? Subject,
+        string? BodyText,
+        DateTimeOffset ReceivedAt,
+        uint Uid);
+
+    /// <summary>Reads mail from a folder. Abstracted so tests feed canned summaries
+    /// (the live MailKit/Gmail path is gated on Julian's App Password).</summary>
+    public interface IGmailMailReader
+    {
+        /// <summary>Fetch messages with UID &gt; <paramref name="sinceUid"/> from the configured folder.</summary>
+        Task<IReadOnlyList<MailSummary>> FetchAsync(MailConnection connection, uint sinceUid, CancellationToken ct = default);
+    }
+
+    /// <summary>Outcome of a sync run.</summary>
+    public sealed record SyncResult(int Imported, string? Error);
+}