chore: organize solution into module folders (Core/Server/Drivers/Client/Tooling)

Group all 69 projects into category subfolders under src/ and tests/ so the
Rider Solution Explorer mirrors the module structure. Folders: Core, Server,
Drivers (with a nested Driver CLIs subfolder), Client, Tooling.

- Move every project folder on disk with git mv (history preserved as renames).
- Recompute relative paths in 57 .csproj files: cross-category ProjectReferences,
  the lib/ HintPath+None refs in Driver.Historian.Wonderware, and the external
  mxaccessgw refs in Driver.Galaxy and its test project.
- Rebuild ZB.MOM.WW.OtOpcUa.slnx with nested solution folders.
- Re-prefix project paths in functional scripts (e2e, compliance, smoke SQL,
  integration, install).

Build green (0 errors); unit tests pass. Docs left for a separate pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Server/ZB.MOM.WW.OtOpcUa.Server/appsettings.json

@@ -0,0 +1,26 @@
+{
+  "Serilog": {
+    "MinimumLevel": "Information"
+  },
+  "Node": {
+    "NodeId": "node-dev-a",
+    "ClusterId": "cluster-dev",
+    "ConfigDbConnectionString": "Server=10.100.0.35,14330;Database=OtOpcUaConfig;Integrated Security=True;TrustServerCertificate=True;Encrypt=False;",
+    "LocalCachePath": "config_cache.db"
+  },
+  "Historian": {
+    "Wonderware": {
+      "Enabled": false,
+      "PipeName": "OtOpcUaWonderwareHistorian",
+      "SharedSecret": "",
+      "PeerName": "OtOpcUa-node-dev-a",
+      "DriverInstancePrefix": "galaxy",
+      "ConnectTimeoutSeconds": 10,
+      "CallTimeoutSeconds": 30
+    }
+  },
+  "Galaxy": {
+    "$comment": "PR 7.1 — DefaultBackend selects which factory tooling and migration scripts pick when authoring NEW Galaxy DriverInstance rows. Both factories register at startup so existing rows keep working: 'GalaxyMxGateway' (default since PR 7.1, in-process .NET 10 driver over the mxaccessgw gRPC gateway) and 'Galaxy' (legacy out-of-process Galaxy.Host EXE + named pipe). Legacy registration retires in PR 7.2 once the parity matrix in docs/v2/Galaxy.ParityMatrix.md is fully green on the parity rig.",
+    "DefaultBackend": "GalaxyMxGateway"
+  }
+}