Add registry curation system with role-based moderation

Implement comprehensive moderation system for the CmdForge registry:

- Role-based access control (user, moderator, admin)
- Tool moderation workflow: pending → approved/rejected/removed
- Tool visibility: public, private, unlisted
- Publisher management: ban/unban with token revocation
- Report resolution with configurable actions
- Audit logging for all moderation actions

Database changes:
- Add role, banned columns to publishers table
- Add visibility, moderation_status columns to tools table
- Create audit_log table for accountability

API additions:
- Admin endpoints for tool moderation (approve/reject/remove)
- Publisher management endpoints (ban/unban/role)
- Report resolution endpoint
- Audit log query endpoint

Web UI:
- Admin dashboard with stats overview
- Pending tools queue with approve/reject
- Publisher management with ban/role controls
- Report queue with resolve actions
- Role badge in dashboard sidebar

Existing tools grandfathered as approved, all publishers default to user role.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/cmdforge/web/templates/errors/403.html

@@ -0,0 +1,25 @@
+{% extends "base.html" %}
+
+{% block title %}Access Denied - CmdForge{% endblock %}
+
+{% block content %}
+<div class="min-h-[60vh] flex items-center justify-center px-4">
+    <div class="text-center max-w-md">
+        <p class="text-6xl font-bold text-red-600">403</p>
+        <h1 class="mt-4 text-3xl font-bold text-gray-900">Access Denied</h1>
+        <p class="mt-4 text-gray-600">
+            Sorry, you don't have permission to access this page. This area is restricted to administrators and moderators.
+        </p>
+        <div class="mt-8 flex flex-col sm:flex-row items-center justify-center gap-4">
+            <a href="{{ url_for('web.dashboard') }}"
+               class="w-full sm:w-auto inline-flex justify-center items-center px-6 py-3 text-base font-medium text-white bg-indigo-600 rounded-md hover:bg-indigo-700">
+                Go to Dashboard
+            </a>
+            <a href="{{ url_for('web.home') }}"
+               class="w-full sm:w-auto inline-flex justify-center items-center px-6 py-3 text-base font-medium text-gray-700 border border-gray-300 rounded-md hover:bg-gray-50">
+                Go Home
+            </a>
+        </div>
+    </div>
+</div>
+{% endblock %}