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/Models/InboxModels.cs

@@ -0,0 +1,66 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace GerbilManagerWebAPI.Models
+{
+    /// <summary>Triage state of an incoming Gmail request (serialised as string name).</summary>
+    public enum RequestStatus
+    {
+        New = 0,
+        InProgress = 1,
+        Assigned = 2,
+        Answered = 3,
+        Abandoned = 4,
+    }
+
+    /// <summary>
+    /// An incoming inquiry imported from Gmail (INBOX epic). One row per email,
+    /// deduped on the RFC Message-Id.
+    /// </summary>
+    public class Request
+    {
+        [Key]
+        public Guid Id { get; set; }
+
+        /// <summary>RFC 5322 Message-Id — unique; the dedup key.</summary>
+        public required string GmailMessageId { get; set; }
+        /// <summary>Gmail conversation id (X-GM-THRID).</summary>
+        public string? ThreadId { get; set; }
+        public string? InReplyToMessageId { get; set; }
+        public string? ReferencesHeader { get; set; }
+
+        public required string FromAddress { get; set; }
+        public string? FromName { get; set; }
+        public string? Subject { get; set; }
+        public string? BodyText { get; set; }
+        public DateTimeOffset ReceivedAt { get; set; }
+
+        public RequestStatus Status { get; set; } = RequestStatus.New;
+
+        public Guid? AssignedContactId { get; set; }
+        public Contact? AssignedContact { get; set; }
+
+        /// <summary>AI/edited draft reply (INBOX-2); send is INBOX-3. Null until drafted.</summary>
+        public string? DraftReply { get; set; }
+        public DateTimeOffset? AnsweredAt { get; set; }
+    }
+
+    /// <summary>
+    /// Singleton mail configuration (INBOX epic). The Gmail App Password is stored
+    /// ENCRYPTED at rest (ASP.NET Data Protection) and never returned over the wire.
+    /// </summary>
+    public class MailSettings
+    {
+        public static readonly Guid SingletonId = new("ab0c0000-0000-0000-0000-000000000001");
+
+        [Key]
+        public Guid Id { get; set; }
+        public string? GmailAddress { get; set; }
+        /// <summary>Data-Protection-encrypted Gmail App Password (never plaintext, never on the wire).</summary>
+        public string? AppPasswordProtected { get; set; }
+        public int PollIntervalMinutes { get; set; } = 15;
+        public string Folder { get; set; } = "INBOX";
+        public bool BackgroundPollEnabled { get; set; }
+        /// <summary>Highest IMAP UID seen, to avoid rescanning the whole folder.</summary>
+        public uint LastUid { get; set; }
+    }
+}