Update AI Assistant disclaimers with data privacy information

[elias-ba]

Description

This PR updates the AI Assistant disclaimers across the application with clearer data privacy information.

• Clarify that messages are stored on OpenFn servers and temporarily on Anthropic servers (up to 30 days)
• Add note that data is not used to train AI models
• Add link to Anthropic's data handling & retention documentation

Validation steps

1. Open a workflow in the collaborative editor
2. Press Cmd+K to open the AI Assistant
3. If you haven't accepted the disclaimer before, verify the new text: "Messages are stored on OpenFn servers and temporarily on Anthropic servers (up to 30 days) but are not used to train AI models."
4. Click "Read more about this here" and verify it opens Anthropic's data handling page
5. Click the menu button (three dots) → "About the AI Assistant" and verify the About modal has the same updated text and link
6. Test the legacy editor's AI Assistant About page for the same updates

Additional notes for the reviewer

AI Usage

Please disclose how you've used AI in this work (it's cool, we just want to know!):

• Code generation (copilot but not intellisense)
• Learning or fact checking
• Strategy / design
• Optimisation / refactoring
• Translation / spellchecking / doc gen
• Other
• I have not used AI

You can read more details in our Responsible AI Policy

Pre-submission checklist

• I have performed a self-review of my code.
• I have implemented and tested all related authorization policies. (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.03%. Comparing base (96f7ef9) to head (4a14767).
⚠️ Report is 11 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4159      +/-   ##
==========================================
+ Coverage   89.02%   89.03%   +0.01%     
==========================================
  Files         425      425              
  Lines       19605    19605              
==========================================
+ Hits        17453    17456       +3     
+ Misses       2152     2149       -3     

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