feat: add config processor mapping parsed config to NatsOptions

Port of Go server/opts.go processConfigFileLine switch. Maps parsed
NATS config dictionaries to NatsOptions fields including:
- Core options (port, host, server_name, limits, ping, write_deadline)
- Logging (debug, trace, logfile, log rotation)
- Authorization (single user, users array with permissions)
- TLS (cert/key/ca, verify, pinned_certs, handshake_first)
- Monitoring (http_port, https_port, http/https listen, base_path)
- Lifecycle (lame_duck_duration/grace_period)
- Server tags, file paths, system account options

Includes error collection (not fail-fast), duration parsing (ms/s/m/h
strings and numeric seconds), host:port listen parsing, and 56 tests
covering all config sections plus validation edge cases.

tests/NATS.Server.Tests/NATS.Server.Tests.csproj

@@ -21,6 +21,10 @@
     <Using Include="Shouldly" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Update="TestData\**\*" CopyToOutputDirectory="PreserveNewest" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\..\src\NATS.Server\NATS.Server.csproj" />
   </ItemGroup>