Fix: emoji picker toggles reactions consistently with message clicks

[rohitbansal2005]

Fix: Emoji picker toggles reactions consistently

Acceptance Criteria fulfillment

• Clicking the same emoji in the picker removes the reaction if the user already reacted.
• Clicking existing message reactions still toggles correctly.
• Toggle logic unified for emoji picker and message reactions.

Fixes #1245

Video.Project.1.mp4

PR Test Details

Note: The PR will be ready for live testing at https://rocketchat.github.io/EmbeddedChat/pulls/pr-1246 after approval.

Testing Steps:

1. Open a message and react with an emoji using the picker.
2. Click the same emoji again → reaction should be removed.
3. Click the same emoji on the message → reaction toggles correctly.
4. Confirm reactions behave identically whether using picker or message click.

[CLAassistant]

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