refactor: restructure mytoolkit with new subcommands and md-to-pdf improvements

- Add new subcommands: convert, preflight, server, templates, webpage
- Migrate config from bin/config.json to ~/.config/mytoolkit
- Fix expand_bookmarks to modify writer objects instead of reader
- Improve md_to_pdf with CJK bookmark support
- Update README and project metadata

bin/commands/templates.py

@@ -0,0 +1,77 @@
+"""Templates registry CLI."""
+
+from pathlib import Path
+
+import click
+
+from bin import templates_registry
+
+
+@click.group(name="templates")
+def templates_cmd():
+    """Manage external templates registry."""
+    pass
+
+
+@templates_cmd.command("register")
+@click.argument("path", type=click.Path(exists=True, file_okay=False, dir_okay=True))
+def templates_register(path):
+    """Register a directory as the templates root."""
+    resolved = templates_registry.set_root(Path(path))
+    click.secho(f"Registered: {resolved}", fg="green")
+
+
+@templates_cmd.command("show")
+def templates_show():
+    """Show the current registry and available templates."""
+    if not templates_registry.CONFIG_PATH.exists():
+        click.echo("No registry. Run: mytoolkit templates register <path>")
+        return
+
+    import json
+
+    with open(templates_registry.CONFIG_PATH, encoding="utf-8") as f:
+        data = json.load(f)
+    raw = data.get("dir")
+    click.echo(f"Registry: {templates_registry.CONFIG_PATH}")
+    click.echo(f"Root:     {raw}")
+
+    if not raw or not Path(raw).is_dir():
+        click.secho("(root path missing)", fg="red")
+        return
+
+    root = Path(raw)
+    pdf_dir = root / "md-to-pdf"
+    docx_dir = root / "md-to-docx"
+
+    click.echo("\nmd-to-pdf:")
+    if pdf_dir.is_dir():
+        entries = sorted(
+            (p.name, p / "template.typ")
+            for p in pdf_dir.iterdir()
+            if (p / "template.typ").exists()
+        )
+        if not entries:
+            click.echo("  (none)")
+        else:
+            width = max(len(n) for n, _ in entries)
+            for name, path in entries:
+                click.echo(f"  - {name:<{width}}  {path}")
+    else:
+        click.secho("  (subdirectory missing)", fg="yellow")
+
+    click.echo("\nmd-to-docx:")
+    if docx_dir.is_dir():
+        entries = sorted(
+            (p.name, p / "template.docx")
+            for p in docx_dir.iterdir()
+            if (p / "template.docx").exists()
+        )
+        if not entries:
+            click.echo("  (none)")
+        else:
+            width = max(len(n) for n, _ in entries)
+            for name, path in entries:
+                click.echo(f"  - {name:<{width}}  {path}")
+    else:
+        click.secho("  (subdirectory missing)", fg="yellow")