feat(phase-2): implement domain verification system

Implements complete domain verification flow with:
- rel=me link verification service
- HTML fetching with security controls
- Rate limiting to prevent abuse
- Email validation utilities
- Authorization and verification API endpoints
- User-facing templates for authorization and verification flows

This completes Phase 2: Domain Verification as designed.

Tests:
- All Phase 2 unit tests passing
- Coverage: 85% overall
- Migration tests updated

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/gondulf/templates/authorize.html

@@ -0,0 +1,30 @@
+{% extends "base.html" %}
+
+{% block title %}Authorization Request - Gondulf{% endblock %}
+
+{% block content %}
+<h1>Authorization Request</h1>
+
+<p>The application <strong>{{ client_id }}</strong> wants to authenticate you.</p>
+
+{% if scope %}
+<p>Requested permissions: <code>{{ scope }}</code></p>
+{% endif %}
+
+<p>You will be identified as: <strong>{{ me }}</strong></p>
+
+{% if error %}
+<p class="error">{{ error }}</p>
+{% endif %}
+
+<form method="POST" action="/authorize/consent">
+    <input type="hidden" name="client_id" value="{{ client_id }}">
+    <input type="hidden" name="redirect_uri" value="{{ redirect_uri }}">
+    <input type="hidden" name="state" value="{{ state }}">
+    <input type="hidden" name="code_challenge" value="{{ code_challenge }}">
+    <input type="hidden" name="code_challenge_method" value="{{ code_challenge_method }}">
+    <input type="hidden" name="scope" value="{{ scope }}">
+    <input type="hidden" name="me" value="{{ me }}">
+    <button type="submit">Authorize</button>
+</form>
+{% endblock %}