Effective config, hosts/addn-hosts logic, test harness status & logs

- EffectiveDnsmasqConfig: overridable single-value options (no-hosts, addn-hosts,
  flags, dhcp-leasefile, cache-size, port, etc.) from dnsmasq source/docs.
- Hosts UI: allow editing when no-hosts but SystemHostsPath is in addn-hosts;
  HostsController and Hosts.razor check pathInAddnHosts.
- Config comments: managed file ensures one addn-hosts line in our file only;
  DnsmasqOptions/validator docs for SystemHostsPath and addn-hosts.
- Test harness: dnsmasq logs to /data/dnsmasq.log (log-facility + log-queries in
  dnsmasq-test.conf); entrypoint touches log file for write access.
- dnsmasq-status.sh: simulates systemctl status output in container (ps/pgrep);
  Dockerfile copies and chmod +x; StatusShowCommand/LogsCommand use script and
  tail /data/dnsmasq.log.
- Project: Models/Config namespace, typed HTTP clients, combined DHCP+Leases
  page, ProcessRunner, shared models (PascalCase).

src/DnsmasqWebUI/Controllers/ConfigController.cs

@@ -1,4 +1,5 @@
 using DnsmasqWebUI.Models;
+using DnsmasqWebUI.Models.Config;
 using DnsmasqWebUI.Services.Abstractions;
 using Microsoft.AspNetCore.Mvc;
 
@@ -49,7 +50,7 @@ public class ConfigController : ControllerBase
         }
     }
 
-    /// <summary>Writes the full managed config file (ensures one addn-hosts line = HostsPath), then optionally triggers reload.</summary>
+    /// <summary>Writes the full managed config file, then optionally triggers reload. When SystemHostsPath is configured, the managed file is updated so it contains exactly one addn-hosts line pointing to that path (so dnsmasq loads the editable hosts file); other config files may have additional addn-hosts lines.</summary>
     [HttpPut("managed")]
     public async Task<ActionResult<object>> PutManaged([FromBody] List<DnsmasqConfLine>? lines, CancellationToken ct)
     {