feat(content-server): scaffold SVSim.ContentServer

New ASP.NET Core 8 web project, standalone (no project references). Serves
the CDN-mirror tree from a configured root via UseStaticFiles mounted at
/dl/, with ServeUnknownFileTypes=true + DefaultContentType=octet-stream
since blob filenames are bare MD5 hashes with no extension and asset
extensions (.unity3d/.acb/.usm) aren't in the default MIME map.

Configuration: SVSIM_CONTENT_ROOT env var (or Content:Root in appsettings,
or --Content:Root cli arg) points at the asset root containing the dl/
subdirectory. The asset root is populated by data_dumps/scripts/
content_cdn_mirror.py in the outer repo (~22 GB Eng+Jpn).

Listens on port 5149 (distinct from EmulatedEntrypoint's 5148). Lightweight
request logging via inline middleware emits status/method/path/ms for every
request. /health returns "ok".

End-to-end smoke verified against the populated working copy at
4670rPsPMVlRTd2:
- Both lang tier-1s served (Eng 1013b / Jpn 955b), MD5s match live CDN.
- A category manifest (bg_assetmanifest Eng) served + verified.
- A 4.5 MB font asset bundle served + MD5-verified.
- A Jpn voice from Sound/Jpn/ served + MD5-verified.
- Hardlinked content (master_ai_ally_common.unity3d, hash shared across
  langs) served identically from both Resource/Eng/ and Resource/Jpn/.
- 404 for missing blobs (correct).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

DCGEngine.sln

@@ -15,6 +15,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SVSim.BattleEngine", "SVSim
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SVSim.BattleEngine.Tests", "SVSim.BattleEngine.Tests\SVSim.BattleEngine.Tests.csproj", "{68F3F596-CAD5-4326-8779-AD8C7BD20CDA}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SVSim.ContentServer", "SVSim.ContentServer\SVSim.ContentServer.csproj", "{AC3897E1-7745-49D0-BFA1-7D859D317C07}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -49,5 +51,9 @@ Global
 		{68F3F596-CAD5-4326-8779-AD8C7BD20CDA}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{68F3F596-CAD5-4326-8779-AD8C7BD20CDA}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{68F3F596-CAD5-4326-8779-AD8C7BD20CDA}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AC3897E1-7745-49D0-BFA1-7D859D317C07}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AC3897E1-7745-49D0-BFA1-7D859D317C07}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AC3897E1-7745-49D0-BFA1-7D859D317C07}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AC3897E1-7745-49D0-BFA1-7D859D317C07}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

SVSim.ContentServer/Program.cs

@@ -0,0 +1,87 @@
+using Microsoft.Extensions.FileProviders;
+
+namespace SVSim.ContentServer;
+
+// SVSim.ContentServer — server #3 of the 4-server topology.
+//
+// Dumb static-file host serving the Shadowverse asset CDN tree. The CDN is
+// plain HTTP, no auth, content-addressed by MD5 in the Resource/Sound trees
+// and name-keyed under Manifest/{resver}/{lang}/{plat}/. We mirror the URL
+// structure on disk and mount UseStaticFiles directly at /dl/.
+//
+// Required runtime config:
+//   SVSIM_CONTENT_ROOT  env var pointing at the asset root (must contain a
+//                       dl/ subdirectory built by data_dumps/scripts/
+//                       content_cdn_mirror.py).
+//
+// Alternatively the same path may be set in appsettings.json under
+// "Content:Root", or passed on the command line as --Content:Root=<path>.
+public class Program
+{
+    public static void Main(string[] args)
+    {
+        var builder = WebApplication.CreateBuilder(args);
+
+        // Env var takes priority — it's the canonical knob per the spec docs.
+        var contentRoot = Environment.GetEnvironmentVariable("SVSIM_CONTENT_ROOT")
+            ?? builder.Configuration["Content:Root"];
+
+        if (string.IsNullOrWhiteSpace(contentRoot))
+        {
+            Console.Error.WriteLine(
+                "SVSim.ContentServer: no content root configured. Set SVSIM_CONTENT_ROOT " +
+                "env var, Content:Root in appsettings, or pass --Content:Root=<path>.");
+            Environment.Exit(2);
+        }
+
+        contentRoot = Path.GetFullPath(contentRoot);
+        var dlRoot = Path.Combine(contentRoot, "dl");
+
+        if (!Directory.Exists(dlRoot))
+        {
+            Console.Error.WriteLine(
+                $"SVSim.ContentServer: content root '{contentRoot}' does not contain a 'dl' " +
+                "subdirectory. Run data_dumps/scripts/content_cdn_mirror.py to populate.");
+            Environment.Exit(2);
+        }
+
+        var app = builder.Build();
+        var logger = app.Services.GetRequiredService<ILogger<Program>>();
+
+        // Request logging for first-light visibility. Registered before
+        // UseStaticFiles so it observes the static responses too.
+        app.Use(async (context, next) =>
+        {
+            var sw = System.Diagnostics.Stopwatch.StartNew();
+            await next();
+            sw.Stop();
+            logger.LogInformation("{Status} {Method} {Path} ({Elapsed}ms)",
+                context.Response.StatusCode,
+                context.Request.Method,
+                context.Request.Path.Value,
+                sw.ElapsedMilliseconds);
+        });
+
+        // ServeUnknownFileTypes=true is REQUIRED. Blob filenames are bare MD5
+        // hashes with no extension; asset/sound/movie extensions (.unity3d,
+        // .acb, .awb, .usm, .lz4) aren't in the default MIME map. The client
+        // doesn't care about Content-Type, but it does care about getting
+        // non-zero bytes.
+        app.UseStaticFiles(new StaticFileOptions
+        {
+            FileProvider = new PhysicalFileProvider(dlRoot),
+            RequestPath = "/dl",
+            ServeUnknownFileTypes = true,
+            DefaultContentType = "application/octet-stream",
+        });
+
+        app.MapGet("/health", () => "ok");
+
+        logger.LogInformation("Content root: {Root}", dlRoot);
+        logger.LogInformation("Serving /dl/* from this root. Manifests are under " +
+                              "/dl/Manifest/{{resver}}/{{lang}}/{{plat}}/; blob trees are " +
+                              "content-addressed under /dl/Resource/ and /dl/Sound/.");
+
+        app.Run();
+    }
+}

SVSim.ContentServer/Properties/launchSettings.json

@@ -0,0 +1,15 @@
+{
+  "$schema": "http://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": false,
+      "applicationUrl": "http://localhost:5149",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development",
+        "SVSIM_CONTENT_ROOT": "C:\\Users\\m\\Documents\\SVSim\\Shadowverse_Assets_Working"
+      }
+    }
+  }
+}

SVSim.ContentServer/SVSim.ContentServer.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <InvariantGlobalization>true</InvariantGlobalization>
+    <RootNamespace>SVSim.ContentServer</RootNamespace>
+  </PropertyGroup>
+
+</Project>

SVSim.ContentServer/appsettings.json

@@ -0,0 +1,12 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*",
+  "Content": {
+    "Root": ""
+  }
+}