Add Flask admin API and live preview endpoint

admin_app.py

@@ -0,0 +1,87 @@
+import yaml
+from flask import Flask, jsonify, request, Response, abort
+
+import build  # reuse your existing static builder logic
+
+app = Flask(__name__)
+
+
+def list_pages():
+    """
+    Return a lightweight list of pages for a sidebar etc.
+    Uses build.load_pages() from the existing builder.
+    """
+    pages = build.load_pages()
+    result = []
+    for p in pages:
+        result.append({
+            "slug": p.get("slug", ""),
+            "title": p.get("title", ""),
+            "language": p.get("language", "de"),
+        })
+    result.sort(key=lambda x: x["slug"])
+    return result
+
+
+@app.get("/api/pages")
+def api_list_pages():
+    return jsonify(list_pages())
+
+
+@app.get("/api/pages/<slug>")
+def api_get_page(slug):
+    try:
+        page, path = build.load_page_by_slug(slug)
+    except FileNotFoundError:
+        abort(404, description="Page not found")
+    return jsonify(page)
+
+
+@app.put("/api/pages/<slug>")
+def api_save_page(slug):
+    """
+    Save page JSON back as YAML. For now we trust the structure,
+    since the admin UI is under our control.
+    """
+    try:
+        _, path = build.load_page_by_slug(slug)
+    except FileNotFoundError:
+        abort(404, description="Page not found")
+
+    new_page = request.get_json(force=True, silent=False)
+    if not isinstance(new_page, dict):
+        abort(400, description="Expected JSON object")
+
+    # Ensure slug consistency
+    new_page.setdefault("slug", slug)
+
+    with open(path, "w", encoding="utf-8") as f:
+        yaml.safe_dump(
+            new_page,
+            f,
+            allow_unicode=True,
+            sort_keys=False,
+            width=1000,
+        )
+
+    return ("", 204)
+
+
+@app.get("/preview/<slug>/")
+def preview_page(slug):
+    """
+    Render HTML for a single page using existing Jinja templates.
+    No disk write: we render directly from the current YAML content.
+    """
+    try:
+        page, _ = build.load_page_by_slug(slug)
+    except FileNotFoundError:
+        abort(404, description="Page not found")
+
+    html = build.render_page(page)
+    return Response(html, mimetype="text/html")
+
+
+if __name__ == "__main__":
+    # For development; in production we'll run this with gunicorn and Caddy as reverse proxy.
+    app.run(host="127.0.0.1", port=8075, debug=True)