refactor: standardize project names to Musify.* and flatten layout

- Flatten nested per-repo folders into flat Musify.* projects at root
- Rename assemblies/csproj: Domain->Musify.Domain, Application->Musify.Application,
  Infrastructure->Musify.Infrastructure, WebApi->Musify.Api, Worker->Musify.Worker,
  StreamingGateway->Musify.StreamingGateway
- Rename WebApi.* namespaces to Musify.Api.*
- Update all ProjectReference paths and the solution file
- Consolidate stray per-repo dotfiles; add root .gitattributes
- Move flutter client out to _archive

Musify.StreamingGateway/appsettings.Development.json

@@ -0,0 +1,32 @@
+{
+  "StreamTicket": {
+    "PublicKeyPath": "D:\\weed\\stream_public.pem",
+    "Audience": "media-gateway",
+    "Issuer": "musify-webapi",
+    "QueryParameterName": "t",
+    "MediaPathPrefix": "/media"
+  },
+
+  "Cors": {
+    "AllowedOrigins": [ "http://localhost:5173", "http://localhost:3000" ]
+  },
+
+  "ReverseProxy": {
+    "Routes": {
+      "media": {
+        "ClusterId": "seaweed-filer",
+        "Match": { "Path": "/media/{**rest}" },
+        "Transforms": [
+          { "PathPattern": "/buckets/webapi-storage/{**rest}" }
+        ]
+      }
+    },
+    "Clusters": {
+      "seaweed-filer": {
+        "Destinations": {
+          "filer": { "Address": "http://localhost:8888/" }
+        }
+      }
+    }
+  }
+}