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/Cms/SiteSnapshotService.cs

@@ -0,0 +1,124 @@
+using System.Text.Json.Nodes;
+using GerbilManagerWebAPI.Models;
+using Microsoft.EntityFrameworkCore;
+
+namespace GerbilManagerWebAPI.Cms
+{
+    /// <summary>
+    /// Builds the full CMS snapshot consumed by the static site renderer (WEB-1). The
+    /// abgabetiere page's auto AbgabetiereList block is resolved here from live ForSale
+    /// animals — nothing private is ever exposed (publish = snapshot of public content).
+    /// </summary>
+    public sealed class SiteSnapshotService
+    {
+        private readonly ApplicationContext _db;
+
+        public SiteSnapshotService(ApplicationContext db) => _db = db;
+
+        public async Task<JsonObject> BuildAsync()
+        {
+            var site = await _db.Sites.AsNoTracking().FirstOrDefaultAsync()
+                       ?? new Site { Id = Site.SingletonId };
+            var pages = await _db.Pages.AsNoTracking().Include(p => p.Blocks).ToListAsync();
+            var pageById = pages.ToDictionary(p => p.Id);
+
+            var navOrder = new JsonArray();
+            foreach (var id in site.NavOrder)
+                if (pageById.TryGetValue(id, out var p))
+                    navOrder.Add(p.Slug);
+
+            JsonArray? forSale = null;   // resolved lazily, reused across blocks
+
+            int NavIndex(Guid id) { var i = site.NavOrder.IndexOf(id); return i < 0 ? int.MaxValue : i; }
+
+            var pagesArr = new JsonArray();
+            foreach (var page in pages.OrderBy(p => NavIndex(p.Id)).ThenBy(p => p.Slug))
+            {
+                var blocks = new JsonArray();
+                foreach (var b in page.Blocks.OrderBy(b => b.Order))
+                {
+                    var data = JsonNode.Parse(string.IsNullOrWhiteSpace(b.Data) ? "{}" : b.Data) as JsonObject
+                               ?? new JsonObject();
+                    if (b.Type == BlockType.AbgabetiereList && AsString(data["mode"]) == "auto")
+                    {
+                        forSale ??= await BuildForSaleAsync();
+                        data["animals"] = forSale.DeepClone();
+                    }
+                    blocks.Add(new JsonObject
+                    {
+                        ["id"] = b.Id.ToString(),
+                        ["order"] = b.Order,
+                        ["type"] = b.Type.ToString(),
+                        ["data"] = data,
+                    });
+                }
+                pagesArr.Add(new JsonObject
+                {
+                    ["slug"] = page.Slug,
+                    ["title"] = page.Title,
+                    ["seoDescription"] = page.SeoDescription,
+                    ["status"] = page.Status.ToString(),
+                    ["blocks"] = blocks,
+                });
+            }
+
+            return new JsonObject
+            {
+                ["site"] = new JsonObject
+                {
+                    ["defaultLocale"] = site.DefaultLocale,
+                    ["navOrder"] = navOrder,
+                },
+                ["pages"] = pagesArr,
+            };
+        }
+
+        private async Task<JsonArray> BuildForSaleAsync()
+        {
+            var animals = await _db.Gerbils.AsNoTracking()
+                .Where(g => g.Status == GerbilStatus.ForSale)
+                .OrderBy(g => g.Name)
+                .Select(g => new
+                {
+                    g.Id,
+                    g.Name,
+                    Farbschlag = g.ColorVariety != null ? g.ColorVariety.Name : null,
+                    // group = Becken (enclosure) name — matches how the Abgabe composer
+                    // groups ForSale animals by enclosure-mates (god ruling). null = single.
+                    Group = g.Enclosure != null ? g.Enclosure.Name : null,
+                })
+                .ToListAsync();
+
+            var ids = animals.Select(a => a.Id).ToList();
+            var photos = await _db.GerbilPhotos.AsNoTracking()
+                .Where(p => ids.Contains(p.GerbilId))
+                .OrderBy(p => p.SortOrder)
+                .Select(p => new { p.GerbilId, p.FileName })
+                .ToListAsync();
+            var photosByGerbil = photos
+                .GroupBy(p => p.GerbilId)
+                .ToDictionary(g => g.Key, g => g.Select(x => $"/photos/files/{x.FileName}").ToList());
+
+            var arr = new JsonArray();
+            foreach (var a in animals)
+            {
+                var photoArr = new JsonArray();
+                if (photosByGerbil.TryGetValue(a.Id, out var urls))
+                    foreach (var u in urls) photoArr.Add(u);
+
+                arr.Add(new JsonObject
+                {
+                    ["name"] = a.Name,
+                    ["farbschlag"] = a.Farbschlag,
+                    ["group"] = a.Group,
+                    ["photos"] = photoArr,
+                    ["aiSaleText"] = null,   // populated by WEB-5 once a Gemini key exists
+                });
+            }
+            return arr;
+        }
+
+        private static string? AsString(JsonNode? node) =>
+            node is JsonValue v && v.TryGetValue<string>(out var s) ? s : null;
+    }
+}