ui: Improve Damus Purple presentation in side view

[ericholguin]

Summary

This PR simply replaces the purple ostrich in the side view with the Damus Logo.
As well as adding a gradient to the Purple text.
I think this better represents Damus Purple.

Changelog-Changed: Changed Damus Purple Side View logo and text

Checklist

• I have read (or I am familiar with) the Contribution Guidelines
• I have tested the changes in this PR
• I have profiled the changes to ensure there are no performance regressions, or I do not need to profile the changes.
  • Utilize Xcode profiler to measure performance impact of code changes. See https://developer.apple.com/videos/play/wwdc2025/306
  • If not needed, provide reason:
    This is simply a cosmetic change
• I have opened or referred to an existing github issue related to this change.
• My PR is either small, or I have split it into smaller logical commits that are easier to review
• I have added the signoff line to all my commits. See Signing off your work
• I have added appropriate changelog entries for the changes in this PR. See Adding changelog entries
  • I do not need to add a changelog entry. Reason: [Please provide a reason]
• I have added appropriate Closes: or Fixes: tags in the commit messages wherever applicable, or made sure those are not needed. See Submitting patches

Test report

Please provide a test report for the changes in this PR. You can use the template below, but feel free to modify it as needed.

Device: [Please specify the device you used for testing]
iPhone 13 mini

iOS: [Please specify the iOS version you used for testing]
17.2

Damus: [Please specify the Damus version or commit hash you used for testing]
1.15 (1) 8122a8a

Setup: [Please provide a brief description of the setup you used for testing, if applicable]
XCode Simulator

Steps: [Please provide a list of steps you took to test the changes in this PR]
View new logo and text in dark/light mode in side view

Results:

• PASS
• Partial PASS
  • Details: [Please provide details of the partial pass]

Other notes

[Please provide any other information that you think is relevant to this PR.]