Implement product selection landing page (Feature 002)

Adds landing page at root URL (/) that displays all active products with links to feedback submission forms. This replaces the requirement for users to know direct product URLs.

Changes:
- Added Product.load_active() method to filter and sort active products alphabetically
- Created landing route blueprint with error handling and structured logging
- Registered landing blueprint in app factory, replacing old index route
- Created landing page template with product list and empty state
- Added comprehensive contract tests (6 tests) covering active products, filtering, sorting, XSS prevention
- Added integration test for complete user flow from landing page to submission form

All 7 tests pass. User Story 1 (P1 - MVP) complete.

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

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

app/templates/landing/index.html

@@ -0,0 +1,37 @@
+{% extends "base.html" %}
+
+{% block title %}Select Product - Reklamator{% endblock %}
+
+{% block content %}
+<h1>Submit Feedback</h1>
+
+{% if products %}
+    <p>Select a product to share your feedback, report issues, or suggest improvements.</p>
+
+    <div style="margin-top: 30px;">
+        {% for product in products %}
+            <div style="background-color: #f8f9fa; padding: 20px; border-radius: 4px; margin-bottom: 15px; border-left: 4px solid #3498db;">
+                <h2 style="margin-top: 0; margin-bottom: 10px; font-size: 1.3em;">
+                    {{ product.name }}
+                </h2>
+
+                {% if product.description %}
+                    <p style="color: #666; margin-bottom: 15px;">{{ product.description }}</p>
+                {% endif %}
+
+                <a href="{{ url_for('submission.form', product_slug=product.submission_url_slug) }}"
+                   class="btn"
+                   style="display: inline-block;">
+                    Submit Feedback
+                </a>
+            </div>
+        {% endfor %}
+    </div>
+{% else %}
+    <div style="background-color: #fff3cd; padding: 20px; border-radius: 4px; border-left: 4px solid #ffc107; margin-top: 20px;">
+        <p style="margin: 0; color: #856404;">
+            No products are currently accepting feedback. Please check back later.
+        </p>
+    </div>
+{% endif %}
+{% endblock %}