Implement MVP: Anonymous feedback submission (User Story 1)

Complete implementation of Phase 1-3 (64 tasks):
- Phase 1: Project setup with Flask, pytest, configuration
- Phase 2: Core infrastructure (auth, models, services, testing)
- Phase 3: Anonymous feedback submission with file uploads

Features:
- Anonymous feedback submission (text and/or up to 3 file attachments)
- Multi-language support (any language accepted)
- File validation (type, size) and virus scanning (ClamAV)
- Product management with active/archived status
- File-based storage with YAML metadata
- User authentication system (Flask-Login)
- CSRF protection and rate limiting
- Test coverage: 10 passing tests (contract + integration)

Security:
- No IP address logging (FR-055 compliance)
- File type whitelist and size limits (10MB max)
- Virus scanning with graceful degradation
- Filename sanitization and secure storage

Test Results:
- 8 contract tests passed
- 2 integration tests passed
- End-to-end workflow verified

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

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

app/templates/auth/login.html

@@ -0,0 +1,25 @@
+{% extends "base.html" %}
+
+{% block title %}Login - Reklamator{% endblock %}
+
+{% block content %}
+<h1>Login</h1>
+
+<form method="POST">
+    <div class="form-group">
+        <label for="username">Username</label>
+        <input type="text" id="username" name="username" required autofocus>
+    </div>
+
+    <div class="form-group">
+        <label for="password">Password</label>
+        <input type="password" id="password" name="password" required>
+    </div>
+
+    <button type="submit">Login</button>
+</form>
+
+<p style="margin-top: 20px;">
+    <a href="{{ url_for('submission.form') }}">Return to feedback submission</a>
+</p>
+{% endblock %}