fix: make community meetings dropdown keyboard accessible

[airajena]

What this does

The community meetings dropdown (src/components/utilities/DropDown) used a clickable <div> for its toggle, so it couldn't be reached or operated with the keyboard, and wasn't exposed as an interactive control to screen readers.

• Replaced the <div> toggle with a <button>, matching the pattern already used in the sibling DropdownButton component.
• Added aria-expanded and aria-controls so assistive tech can tell when the options panel is open.
• Added an Escape key handler to close the dropdown.

Testing

• yarn typecheck and yarn build both pass.
• Manually checked the community meetings dropdown still opens and closes correctly with both mouse and keyboard.

Fixes #687

Checklist

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• [ x] Referenced issues using Fixes: #00000 in commit message (if applicable)
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