Effective config: conntrack as flag; avoid key-only directives for empty non-flag values

- Model conntrack as Flag (parser, config bool, cache, registry FlagValueDisplay)
- Apply: for non-flag options with empty/invalid value, remove existing line
  and never write key-only directive (was producing malformed option= without value)

src/DnsmasqWebUI/Components/EffectiveConfig/Composition/EffectiveConfigSection.razor.css

@@ -211,6 +211,11 @@
     word-break: break-word;
 }
 
+/* Row-level ok/cancel (and revert) for multi-value: right-align on the row below the list */
+::deep .ec-field .ec-field-value-multi + .status-badge-inline {
+    margin-left: auto;
+}
+
 ::deep .ec-field-value-list {
     margin: 0;
     padding-left: 1.25rem;

src/DnsmasqWebUI/Infrastructure/Helpers/Config/EffectiveConfigOptionKindMap.cs

@@ -286,7 +286,7 @@ public static class EffectiveConfigParserBehaviorMap
             [DnsmasqConfKeys.LogDhcp] = EffectiveConfigParserBehavior.Flag,
             [DnsmasqConfKeys.KeepInForeground] = EffectiveConfigParserBehavior.Flag,
             [DnsmasqConfKeys.NoDaemon] = EffectiveConfigParserBehavior.Flag,
-            [DnsmasqConfKeys.Conntrack] = EffectiveConfigParserBehavior.LastWins,
+            [DnsmasqConfKeys.Conntrack] = EffectiveConfigParserBehavior.Flag,
         };
 
     /// <summary>Returns LastWins, Flag, or Multi for the given option name; defaults to LastWins if unknown.</summary>

src/DnsmasqWebUI/Infrastructure/Services/Dnsmasq/Config/ConfigSetCache.cs

@@ -391,8 +391,7 @@ public sealed class ConfigSetCache : IConfigSetCache, IDisposable
         var dhcpScriptPath = string.IsNullOrWhiteSpace(dhcpScriptVal) ? null : DnsmasqConfIncludeParser.ResolvePath(dhcpScriptVal?.Trim(), dhcpScriptDir);
         var (mxTargetVal, _) = ((string?, string?))ParseOptionValue(paths, pathToLines, DnsmasqConfKeys.MxTarget);
         var mxTarget = string.IsNullOrWhiteSpace(mxTargetVal) ? null : mxTargetVal.Trim();
-        var (conntrackVal, _) = ((string?, string?))ParseOptionValue(paths, pathToLines, DnsmasqConfKeys.Conntrack);
-        var conntrack = string.IsNullOrWhiteSpace(conntrackVal) ? null : conntrackVal.Trim();
+        var conntrack = (bool)ParseOptionValue(paths, pathToLines, DnsmasqConfKeys.Conntrack);
 
         return new EffectiveDnsmasqConfig(
             noHosts, addnHosts, hostsdirPath,
@@ -535,7 +534,7 @@ public sealed class ConfigSetCache : IConfigSetCache, IDisposable
         var (_, fastDnsRetrySource) = ((string?, ConfigValueSource?))ParseOptionWithSource(paths, pathToLines, DnsmasqConfKeys.FastDnsRetry, managedFilePath);
         var (_, dhcpScriptPathSource) = ((string?, ConfigValueSource?))ParseOptionWithSource(paths, pathToLines, DnsmasqConfKeys.DhcpScript, managedFilePath);
         var (_, mxTargetSource) = ((string?, ConfigValueSource?))ParseOptionWithSource(paths, pathToLines, DnsmasqConfKeys.MxTarget, managedFilePath);
-        var (_, conntrackSource) = ((string?, ConfigValueSource?))ParseOptionWithSource(paths, pathToLines, DnsmasqConfKeys.Conntrack, managedFilePath);
+        var (_, conntrackSource) = ((bool, ConfigValueSource?))ParseOptionWithSource(paths, pathToLines, DnsmasqConfKeys.Conntrack, managedFilePath);
 
         return new EffectiveConfigSources(
             noHostsSource, addnHostsWithSource.Select(t => new PathWithSource(t.Path, t.Source)).ToList(), hostsdirPathSource,
@@ -718,7 +717,7 @@ public sealed class ConfigSetCache : IConfigSetCache, IDisposable
             LogFacility: null, LogQueries: null, AuthTtl: null, EdnsPacketMax: null, QueryPort: null, PortLimit: null, MinPort: null, MaxPort: null, LogAsync: null, LocalService: null,
             DhcpLeaseMax: null, NegTtl: null, MaxTtl: null, MaxCacheTtl: null, MinCacheTtl: null, DhcpTtl: null,
             TftpRootPath: null, PxePrompt: null, EnableDbus: null, EnableUbus: null, FastDnsRetry: null,
-            DhcpScriptPath: null, MxTarget: null, Conntrack: null
+            DhcpScriptPath: null, MxTarget: null, Conntrack: false
         );
 
     private static EffectiveConfigSources CreateDefaultEffectiveConfigSources() =>

src/DnsmasqWebUI/Infrastructure/Services/Dnsmasq/Config/DnsmasqConfigService.cs

@@ -271,13 +271,23 @@ public class DnsmasqConfigService : IDnsmasqConfigService
                 if (idx >= 0) list.RemoveAt(idx);
                 continue;
             }
+            if (!isFlag)
+            {
+                var v = ToConfValue(c.NewValue);
+                if (string.IsNullOrWhiteSpace(v))
+                {
+                    // Non-flag option with no value: remove existing line if any; never write key-only (malformed).
+                    if (idx >= 0) list.RemoveAt(idx);
+                    continue;
+                }
+            }
             string rawLine;
             if (isFlag)
                 rawLine = confKey;
             else
             {
-                var v = ToConfValue(c.NewValue);
-                rawLine = string.IsNullOrEmpty(v) ? confKey : confKey + "=" + v;
+                var v = ToConfValue(c.NewValue).Trim();
+                rawLine = confKey + "=" + v;
             }
             var newLine = new OtherLine { LineNumber = maxLineNumber + 1, RawLine = rawLine };
             maxLineNumber++;

src/DnsmasqWebUI/Infrastructure/Services/EffectiveConfig/EffectiveConfigRenderFragmentRegistry.cs

@@ -75,6 +75,7 @@ public class EffectiveConfigRenderFragmentRegistry : IEffectiveConfigRenderFragm
         RegisterFlag(EffectiveConfigFieldBuilder.SectionProcess, DnsmasqConfKeys.LogDhcp);
         RegisterFlag(EffectiveConfigFieldBuilder.SectionProcess, DnsmasqConfKeys.KeepInForeground);
         RegisterFlag(EffectiveConfigFieldBuilder.SectionProcess, DnsmasqConfKeys.NoDaemon);
+        RegisterFlag(EffectiveConfigFieldBuilder.SectionProcess, DnsmasqConfKeys.Conntrack);
         RegisterFlag(EffectiveConfigFieldBuilder.SectionDnssec, DnsmasqConfKeys.ProxyDnssec);
 
         // log-queries: dropdown (Off / On / extra / proto / auth).

src/DnsmasqWebUI/Models/Dnsmasq/EffectiveConfig/EffectiveDnsmasqConfig.cs

@@ -139,7 +139,7 @@ public record EffectiveDnsmasqConfig(
     string? FastDnsRetry,
     string? DhcpScriptPath,
     string? MxTarget,
-    string? Conntrack
+    bool Conntrack
 )
 {
     /// <summary>