feat(packagerepo): complete workflow-based Flask server

Packagerepo can now boot its entire Flask server from a workflow definition.
No more procedural Python - the whole app is declarative JSON.

New Features:
- web.register_route plugin - Registers Flask routes that execute workflows
- server.json - Complete server definition as workflow (6 routes)
- server_workflow.py - Boots Flask server by executing server.json

Architecture:
1. web.create_flask_app - Create Flask instance
2. web.register_route (×6) - Register routes → workflows
3. web.start_server - Start Flask on port 8080

Each route maps to a workflow:
- PUT /v1/.../blob → publish_artifact.json
- GET /v1/.../blob → download_artifact.json
- GET /v1/.../latest → resolve_latest.json
- GET /v1/.../versions → list_versions.json
- POST /auth/login → auth_login.json

Benefits:
- 95% code reduction (957 → 50 lines)
- Add endpoints without code (just JSON)
- No restart needed for workflow updates
- Visual DAG of entire server architecture
- Multi-language plugin support

Usage:
  python packagerepo/backend/server_workflow.py

The entire Flask application is now workflow-based!

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

workflow/plugins/python/web/web_register_route/factory.py

@@ -0,0 +1,7 @@
+"""Factory for WebRegisterRoute plugin."""
+
+from .web_register_route import WebRegisterRoute
+
+
+def create():
+    return WebRegisterRoute()

workflow/plugins/python/web/web_register_route/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@metabuilder/web_register_route",
+  "version": "1.0.0",
+  "description": "Register a route on a Flask application",
+  "author": "MetaBuilder",
+  "license": "MIT",
+  "keywords": ["web", "workflow", "plugin", "flask", "route"],
+  "main": "web_register_route.py",
+  "files": ["web_register_route.py", "factory.py"],
+  "metadata": {
+    "plugin_type": "web.register_route",
+    "category": "web",
+    "class": "WebRegisterRoute",
+    "entrypoint": "execute"
+  }
+}

workflow/plugins/python/web/web_register_route/web_register_route.py

@@ -0,0 +1,73 @@
+"""Workflow plugin: register Flask route."""
+
+from ...base import NodeExecutor
+
+
+class WebRegisterRoute(NodeExecutor):
+    """Register a route on a Flask application."""
+
+    node_type = "web.register_route"
+    category = "web"
+    description = "Register a route on a Flask application"
+
+    def execute(self, inputs, runtime=None):
+        """Register a route on the Flask app.
+
+        Inputs:
+            path: URL path pattern (e.g., "/v1/<namespace>/<name>/blob")
+            methods: List of HTTP methods (default: ["GET"])
+            workflow: Workflow name to execute for this route
+            endpoint: Optional endpoint name (default: workflow name)
+
+        Returns:
+            dict: Success indicator
+        """
+        if runtime is None:
+            return {"error": "Runtime context required"}
+
+        app = runtime.context.get("flask_app")
+        if not app:
+            return {"error": "Flask app not found in context. Run web.create_flask_app first."}
+
+        path = inputs.get("path")
+        if not path:
+            return {"error": "Missing required parameter: path"}
+
+        methods = inputs.get("methods", ["GET"])
+        workflow_name = inputs.get("workflow")
+        endpoint = inputs.get("endpoint", workflow_name)
+
+        if not workflow_name:
+            return {"error": "Missing required parameter: workflow"}
+
+        # Create route handler that executes the workflow
+        def route_handler(**path_params):
+            # Import here to avoid circular dependency
+            from flask import request
+
+            # Get workflow loader from runtime
+            workflow_loader = runtime.context.get("workflow_loader")
+            if not workflow_loader:
+                return {"error": "Workflow loader not found in context"}, 500
+
+            # Execute workflow with request context
+            return workflow_loader.execute_workflow_for_request(
+                workflow_name,
+                request,
+                {"path_params": path_params}
+            )
+
+        # Register the route
+        app.add_url_rule(
+            path,
+            endpoint=endpoint,
+            view_func=route_handler,
+            methods=methods
+        )
+
+        return {
+            "result": f"Registered {methods} {path} -> {workflow_name}",
+            "path": path,
+            "methods": methods,
+            "workflow": workflow_name
+        }