Add cookies section to privacy policy

[andreagrandi]

Summary

• Adds a new Section 10 — Cookies to both EN and IT privacy pages, listing the three strictly necessary cookies used (sessionid, csrftoken, django_language) with their purpose and lifetime
• Explains why no consent banner is shown (ePrivacy Directive Art. 5(3) exemption for strictly necessary cookies)
• States explicitly that no tracking, analytics, or advertising cookies are used
• Bumps "Last updated" date to 3 April 2026
• Renumbers the former section 10 (Changes to this policy) to section 11

Test plan

• Verify /privacy/ renders correctly with the new section
• Verify /it/privacy/ renders correctly with the Italian version
• Confirm section numbering is sequential (1–11)