WEB-0: CMS content model + /api/site-snapshot + Page/Block CRUD

- Entities: Site (singleton, navOrder JSON), Page (slug/title/seoDescription/status enum),
  Block (single table, Type enum + Data JSON; RichText=Markdown), Media. Migration
  AddCmsEntities, seeds 6 Jimdo-mirror pages (placeholder Heading each; abgabetiere also an
  auto AbgabetiereList block) + Site singleton nav.
- GET /api/site-snapshot: one JSON doc (site nav + pages + ordered blocks {id,order,type,data});
  AbgabetiereList(auto) resolved from live ForSale gerbils -> {name, farbschlag, group(=Becken),
  photos[urls], aiSaleText:null} (no price per god). SiteSnapshotService.
- CRUD: GET/POST/PUT/DELETE pages; add/update/delete blocks; PUT .../blocks/order reorder.
  Block type allowlisted by enum; data validated as JSON object.

GerbilManagerWebAPI/Models/CmsModels.cs

@@ -0,0 +1,80 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace GerbilManagerWebAPI.Models
+{
+    /// <summary>Publication state of a CMS page (serialised as string name).</summary>
+    public enum PageStatus
+    {
+        Draft = 0,
+        Published = 1,
+    }
+
+    /// <summary>
+    /// CMS block kinds. RichText holds MARKDOWN (sanitised on render). AbgabetiereList is
+    /// dynamic — resolved from live ForSale animals at snapshot time. Serialised as string.
+    /// </summary>
+    public enum BlockType
+    {
+        Heading = 0,
+        RichText = 1,
+        Image = 2,
+        Gallery = 3,
+        ContactInfo = 4,
+        AbgabetiereList = 5,
+    }
+
+    /// <summary>Singleton site settings (WEB epic CMS).</summary>
+    public class Site
+    {
+        /// <summary>Fixed id — there is exactly one Site row.</summary>
+        public static readonly Guid SingletonId = new("5172e000-0000-0000-0000-000000000001");
+
+        [Key]
+        public Guid Id { get; set; }
+        public string DefaultLocale { get; set; } = "de";
+        /// <summary>Ordered page ids for the public nav (JSON list).</summary>
+        public List<Guid> NavOrder { get; set; } = new();
+    }
+
+    /// <summary>A CMS page (one of the public website's pages).</summary>
+    public class Page
+    {
+        [Key]
+        public Guid Id { get; set; }
+        /// <summary>Stable URL slug (e.g. "abgabetiere") — the human key.</summary>
+        public required string Slug { get; set; }
+        public required string Title { get; set; }
+        public string? SeoDescription { get; set; }
+        public PageStatus Status { get; set; } = PageStatus.Draft;
+
+        public ICollection<Block> Blocks { get; } = new List<Block>();
+    }
+
+    /// <summary>
+    /// A content block on a page (single table, discriminated by <see cref="Type"/>).
+    /// Type-specific payload lives in <see cref="Data"/> as JSON (RichText = Markdown).
+    /// </summary>
+    public class Block
+    {
+        [Key]
+        public Guid Id { get; set; }
+        public Guid PageId { get; set; }
+        /// <summary>Explicit ordering within the page (AI tools reorder by this).</summary>
+        public int Order { get; set; }
+        public BlockType Type { get; set; }
+        /// <summary>Type-specific fields as a JSON object string.</summary>
+        public string Data { get; set; } = "{}";
+    }
+
+    /// <summary>A media asset referenced by Image/Gallery blocks.</summary>
+    public class Media
+    {
+        [Key]
+        public Guid Id { get; set; }
+        public required string FileName { get; set; }
+        public required string Url { get; set; }
+        public string? Alt { get; set; }
+        public int? Width { get; set; }
+        public int? Height { get; set; }
+    }
+}