Update goo.gle/a2a-inspector-app

Since using [A2A Python SDK 0.3.0](https://github.com/a2aproject/a2a-python/releases/tag/v0.3.0)+, it might support new A2A card default address (i.e., `/.well-known/agent-card.json`) but I get bellow error with new A2A Server only serving `/.well-known/agent-card.json`.

Please release a new version to [goo.gle/a2a-inspector-app](https://goo.gle/a2a-inspector-app). 🙏

p.s. If backward compatibility is a concern, supporting both could be a viable solution.

The issue mentions an error with the new A2A card default address (/.well-known/agent-card.json) when using A2A Python SDK 0.3.0+. First, examine the codebase to understand how the inspector currently fetches agent cards and handles endpoints. Look for configuration or URL-building logic related to the well-known path. Check if there are existing tests for card fetching to see the expected behavior. The goal is to update the app to support the new endpoint, possibly while maintaining backward compatibility with the old address.

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