Add KLIPY GIF search to message composers

[klopez4212]

Summary

• adds Emoji and GIF tabs to message and forum composers
• supports KLIPY trending/search results and uploads the selected GIF through Buzz's existing media flow
• keeps Emoji Mart aligned with Buzz's theme and picker width

@wesbillman @tlongwell-block — support for GIF search was pretty straightforward to add; this is a working end-to-end implementation.

Next steps before release

Business-side help needed:

• request a KLIPY production API key
• confirm that posting selected GIFs into Buzz media storage is covered by KLIPY's terms
• confirm the required ad model, official attribution, and privacy disclosure

Engineering follow-up after those decisions: wire the production key into release builds, hide the tab when unconfigured, add the official KLIPY branding, and harden pagination and download-size limits.

Validation

• tested trending, search, selection, upload, and light/dark themes in the staging app
• 2,912 desktop unit tests pass
• desktop typecheck, formatting checks, and production build pass
• the broader local Rust gate was attempted but exhausted machine disk; GitHub CI will run the complete gate