feat(chat): Implement full emoji picker with search and categories

[Sayan-pixel]

Summary

Replaced the hardcoded, limited emoji list in the chat composer with a full-featured emoji picker using emoji-picker-element.

• Integrates the full standard system emoji dataset.
• Adds search functionality (by name or keyword).
• Adds category tabs (Smileys, People, Nature, etc.).
• Adds a "Recently used" section that persists locally.
• Implements a click-outside handler to cleanly close the popover.
• Implements an accessibility enhancement so category tabs switch automatically when navigating via keyboard ArrowLeft / ArrowRight.

Linked issue

Closes #303

How to test

1. Open a chat dialog and click the emoji (smile) icon in the composer.
2. Verify the full emoji picker opens and renders correctly.
3. Type a query in the search bar and verify the results filter correctly.
4. Use the ArrowLeft and ArrowRight keys to navigate the category tabs and verify the categories switch instantly.
5. Click an emoji (or press Enter) and verify it is inserted at the exact cursor position in the composer input field.
6. Click anywhere outside the popover (e.g., on the chat messages) and verify the picker closes automatically.

Notes / Risk

• Bundle Size: The impact on bundle size is extremely minimal because emoji-picker-element relies entirely on native system fonts rather than shipping large sprite sheets.
• Dependencies: Added emoji-picker-element as a runtime dependency.

[Copilot]

🟡 Not ready to approve

There are verified runtime/behavioral issues in the new emoji picker event handling (target vs currentTarget, weak typing/guarding) and an unexpected root-level lockfile that likely shouldn’t be committed.

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Pull request overview

This PR upgrades the private chat composer’s emoji UX by replacing the small hardcoded emoji grid with the emoji-picker-element web component to provide a full emoji set with search, categories, and “recently used” behavior (handled by the component).

Changes:

• Replaced the in-template emoji grid with <emoji-picker> and wired selection into the existing caret insertion logic.
• Added keyboard handling for category tab switching and a document click-outside handler to close the popover.
• Added emoji-picker-element as a runtime dependency and updated styles to theme the picker.

File summaries

File	Description
package-lock.json	Adds a new root lockfile (currently empty/likely accidental).
frontend/src/app/pages/private-chat-dialog/private-chat-dialog.component.ts	Integrates emoji-picker-element, updates insertion and popover closing behavior, adds keyboard/click-outside handlers.
frontend/src/app/pages/private-chat-dialog/private-chat-dialog.component.html	Replaces hardcoded emoji buttons with <emoji-picker> and updates focus handling.
frontend/src/app/pages/private-chat-dialog/private-chat-dialog.component.scss	Styles the <emoji-picker> web component and adjusts responsive layout.
frontend/src/app/pages/private-chat-dialog/chat-reactions.ts	Removes the hardcoded CHAT_EMOJIS list.
frontend/package.json	Adds emoji-picker-element dependency.
frontend/package-lock.json	Locks emoji-picker-element dependency.

Review details

Files not reviewed (1)

• frontend/package-lock.json: Generated file

• Files reviewed: 5/7 changed files
• Comments generated: 3
• Review effort level: Lite

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[DenizAltunkapan]

@Sayan-pixel please apply copilots requested changes