Add Frappe Agent marketplace icon

[Dkm0315]

Summary

• add an SVG icon asset for the Frappe Agent marketplace listing
• add icon to the marketplace entry
• add interface.composerIcon to the mirrored plugin manifest

Validation

• parsed .agents/plugins/marketplace.json, plugins.json, and the Frappe Agent plugin manifest with python3 -m json.tool
• parsed the SVG icon with Python XML parser
• git diff --check

Release: https://github.com/Dkm0315/frappe-agent/releases/tag/v0.1.0

[gemini-code-assist]

Code Review

This pull request introduces a new SVG icon for the Frappe Agent plugin and updates the marketplace and plugin configuration files to reference this asset. The reviewer suggested using more unique IDs for the SVG's title and description elements to avoid potential ID collisions and accessibility issues when multiple icons are displayed on the same page.