Update privacy policy to cover feedback form data processing

[Konstantin-Zhukov]

Description

Related: #115

The documentation site's privacy policy (Datenschutzerklärung) does not currently describe the data collected when users submit the feedback form. A new subsection must be added to section 4.2 covering the feedback form, and a duplicate section numbering error (two sections labeled 4.3) must be fixed.

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Problem / Motivation

The feedback form was recently added to the documentation site. It collects a user's feedback message (required) and submits it to a backend which stores it as a public GitHub issue. The current privacy policy has no mention of this data processing. Since the feedback form displays a privacy consent checkbox linking to this policy, the policy must accurately describe what data is collected, how it is used, where it is stored, and the legal basis — otherwise the site is not compliant with DSGVO.

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Proposed Solution

Add a new subsection 4.2.3 Feedback-Formular to src/pages/privacy-policy.mdx (under the existing "Direkte Datensammlung" section) covering:

• Data collected: feedback message
• Purpose: improving documentation quality
• Storage: submitted feedback is stored as public issues on GitHub
• Legal basis: Art. 6 Abs. 1 lit. a DSGVO (explicit consent via checkbox)
• Retention: data is kept until no longer needed for documentation improvement

Additionally, fix the duplicate section numbering: the second section 4.3 (cookies) should be renumbered to 4.4.

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Acceptance Criteria

• New subsection 4.2.3 describes the feedback form data processing in German
• Subsection covers: data collected, purpose, storage location (public GitHub issues), legal basis, retention
• Users are informed that submitted feedback becomes publicly visible on GitHub
• Duplicate section 4.3 numbering is resolved (cookies become 4.4)
• Privacy consent checkbox link in the feedback form remains valid and points to the updated section