docs(guides): apply review feedback to sensitive data guide

[Copilot]

Applied 5 review comments from PR #30 to improve clarity and consistency in the sensitive data processing guide.

Changes:

• GDPR legal basis clarification - Separated distinct legal bases (public interest vs. explicit consent) to avoid ambiguity about when each applies under GDPR
• Section heading specificity - Changed "Similarities" to "Similarities Between TEE, SPE, and TRE" for immediate clarity on what's being compared
• Terminology consistency - Replaced "knowledge worker" with "researcher" to align with usage throughout the document
• Grammar improvements - Changed "There is an offer of tools" to "Provides tools" for parallel structure with other bullet points
• Security guarantee precision - Reworded confidentiality claim from "if environment is compromised" to "aims to maintain confidentiality and protect against compromise" to accurately reflect security posture

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