Remove BepInEx client patcher (DorkNet.ClientPatch)

MelonLoader (DorkNet.ClientMod) is the sole client patcher now:

- delete the DorkNet.ClientPatch project + tools/install-plugin.ps1
- drop the project from DorkNet.sln
- README / deploy docs: present DorkNet.ClientMod (install-melon.ps1)
  as the patcher instead of the BepInEx plugin
- drop the dead install-plugin.ps1 reference from Program.cs's JWT
  error and install-melon.ps1's DRM-fallback hint
- tidy stray 'BepInEx port' comments

Legacy-cleanup paths that REMOVE an old BepInEx install
(install-legacy-client.ps1, build-patcher-zip.ps1's old_plugin_paths)
are kept intentionally.

DorkNet.Server/Controllers/Auth/PhotonCustomAuthController.cs

@@ -10,7 +10,7 @@ namespace DorkNet.Server.Controllers.Auth;
 ///
 /// Photon Cloud sends a GET (or POST) with the parameters the client
 /// attached via <c>AuthenticationValues.AddAuthParameter</c>. The
-/// DorkNet BepInEx plugin (DorkNet.ClientPatch) injects two:
+/// DorkNet client mod (DorkNet.ClientMod) injects two:
 /// <list type="bullet">
 ///   <item><c>userid</c> — the player's DorkNet account id (long).</item>
 ///   <item><c>LoginLock</c> — the per-session GUID stored in
@@ -118,7 +118,7 @@ public class PhotonCustomAuthController(
 
         // Anonymous connect: pre-login Photon region pings + the watch's
         // initial NameServer probe both fire CustomAuth WITHOUT
-        // AuthValues attached (the BepInEx plugin only injects AuthValues
+        // AuthValues attached (the client mod only injects AuthValues
         // once /player/login has run and Core.LocalAccountId is set).
         // Returning ResultCode 1 here lets those bootstrap connects
         // succeed; the actual gameplay session has populated AuthValues

DorkNet.Server/Program.cs

@@ -218,8 +218,7 @@ var jwtSecret = Environment.GetEnvironmentVariable("DORKNET_JWT_SECRET")
     ?? builder.Configuration["Jwt:Secret"]
     ?? throw new InvalidOperationException(
         "JWT secret not configured. Set the DORKNET_JWT_SECRET env var or " +
-        "add `Jwt:Secret` to appsettings.Local.json (the install-plugin.ps1 " +
-        "script generates one automatically on same-machine setup).");
+        "add `Jwt:Secret` to appsettings.Local.json.");
 
 builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
     .AddJwtBearer(opt =>