feat(config): add ConfigResolver with CLI>file>default precedence

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeMailbox/Config/ConfigResolver.cs

@@ -0,0 +1,30 @@
+using ClaudeMailbox.Cli;
+
+namespace ClaudeMailbox.Config;
+
+public static class ConfigResolver
+{
+    public static DaemonConfig Build(string[] serveArgs, FileConfig file)
+    {
+        var cliPort = ParseIntOption(serveArgs, "--port");
+        var cliBind = ClientCommands.GetOption(serveArgs, "--bind");
+        var cliDbPath = ClientCommands.GetOption(serveArgs, "--db-path");
+
+        var port = cliPort ?? file.Port ?? DaemonConfig.DefaultPort;
+        var bind = cliBind ?? file.Bind ?? DaemonConfig.DefaultBindAddress;
+        var dbPathRaw = cliDbPath ?? file.DbPath ?? Paths.DefaultDbPath();
+
+        return new DaemonConfig
+        {
+            Port = port,
+            BindAddress = bind,
+            DbPath = Paths.Expand(dbPathRaw),
+        };
+    }
+
+    private static int? ParseIntOption(string[] args, string name)
+    {
+        var raw = ClientCommands.GetOption(args, name);
+        return int.TryParse(raw, out var v) ? v : null;
+    }
+}