fix(ui): validate optional tool icon URL and add fallback icon in too…

[sahil2448]

BugFix : Added Validation check for TOOL ICON SOURCE Field in Tools Dialogue, and add a default icon image if user has not provided

Related issue

Closes #6369

Summary

This PR improves the Tools icon UX by making Tool Icon Source optional while validating it when provided.

What’s fixed

• Tool Icon Source now validates as an http / https URL only when non-empty.
• Invalid URLs show inline validation feedback and block submit.
• Submitting with an invalid URL shows an error toast.
• Added a default tool icon fallback when the icon URL is empty, invalid, or broken in:
  • Tools card view
  • Tools table/list view

Problem

Previously:

• Any random string could be saved as Tool Icon Source.
• This caused broken icon rendering in Tools views.
• Empty icon source did not have a consistent UI fallback.

Changes

Frontend

ToolDialog.jsx

• Added optional URL validator (http / https only).
• Added inline error text for invalid URL.
• Disabled Add/Save button when URL is invalid.
• Added submit-time snackbar error for invalid URL.
• Kept the field optional, so empty values are allowed.

ToolsListTable.jsx

• Added icon component with onError fallback to default tool.svg.

ItemCard.jsx

• Added optional fallbackIconSrc support for icon rendering.
• Added image fallback behavior for broken icon URLs.

tools/index.jsx

• Passed default tool.svg fallback to tool cards.

Behavior after this PR

• Empty icon source: allowed, default icon shown.
• Valid icon URL: image shown.
• Invalid icon URL: validation error shown, save blocked.

Screen.Recording.2026-05-12.002742.mp4

Testing done

• Created tool with a valid icon URL → save succeeds, icon renders.
• Created tool with invalid text (abc123) in icon source → inline error + save blocked.
• Cleared icon source and saved tool → save succeeds, default icon renders.
• Opened existing tools with bad icon URL → fallback icon displayed.

Scope / Notes

• Frontend-only fix. No backend validation added in this PR.
• No unrelated files changed.

[gemini-code-assist]

Code Review

This pull request introduces a new icon handling mechanism for tools, including fallback icon support and URL validation for tool icons. It adds IconAvatar and ToolIconAvatar components to handle image loading errors and provides a validation utility in ToolDialog to ensure icon sources are valid HTTP/HTTPS URLs. Feedback includes a suggestion to prevent infinite loops in the onError handler if a fallback icon fails, a recommendation to deduplicate the avatar component logic into a shared component, and an optimization for the submit button's disabled state by using existing error state instead of re-validating on every render.