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>

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"
+      }
+    }
+  }
+}