fix: show clear error message when Giphy API requests fail

[oleksandr-nc]

Fixes #37

Changes proposed in this PR:

• Forward actual HTTP status codes from the Giphy API instead of always returning 400
• Display specific error message for rate limits (429): Too many requests to Giphy. Please contact your administrator.
• Display generic error message for other API failures: Failed to load GIFs
• Use AlertIcon for error states to visually distinguish from "No results"

How to easy test this

1. Go to Admin settings → Connected accounts → Giphy integration
2. Set any invalid API key (e.g. abc123) and save
3. Open the GIF picker (e.g. via the smart picker in Text or Talk)
4. Before this PR: you see the sad GIF with "No results" — no indication of what went wrong
5. After this PR: you see an alert icon with "Failed to load GIFs"

Tests from my setup

Invalid API key (unknown error)

Before this PR:

After this PR:

This was emulated, I have changed backend to return always 429 error:

[julien-nc]

Code looks good.