🛡️ Sentinel: [HIGH] Fix CSRF vulnerability

[rauhmaru]

• 🚨 Severity: HIGH
• 💡 Vulnerability: The application had multiple HTML forms that used method="post" to send state-changing requests, but these forms did not include a Cross-Site Request Forgery (CSRF) token.
• 🎯 Impact: Without CSRF protection, an attacker could host a malicious website that submits forged requests to our application's endpoints (e.g., removing or editing products) on behalf of an authenticated or active user session.
• 🔧 Fix: Installed and configured Flask-WTF to enforce global CSRF protection. Included the csrf_token() value in a hidden input across all method="post" forms.
• ✅ Verification: Tests pass and frontend was visually verified to make sure UI is not impacted by this hidden input.

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PR created automatically by Jules for task 17054196976449344421 started by @rauhmaru

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