Feature: Add chat video attachment upload and sending

[mjkatgithub]

Goal

Upload and send videos in chat conversations, so users can share short clips
as message attachments.

Scope

• Add video file selection in the message input (file picker / drag & drop).
• Validate supported MIME types (e.g. video/mp4, video/webm).
• Validate maximum file size before upload (show clear error if exceeded).
• Upload selected video via existing media upload flow/backend endpoint.
• Send uploaded video as a chat message with media metadata.
• Render video messages in timeline with playable preview (controls enabled).
• Show upload/sending states (loading, success, error) in the UI.
• Ensure video messages are handled in message list ordering/reload.
• Add/extend tests for upload, send, and render behavior.

Branch

feature/video-messages

Acceptance Criteria

• User can select a supported video file from message input.
• Unsupported file types are rejected with a user-friendly error.
• Files above max size are rejected with a user-friendly error.
• Valid video uploads successfully and can be sent as a message.
• Sent video message appears in timeline with working playback controls.
• Upload/send loading and error states are visible and understandable.
• Existing text/image message behavior remains unchanged.

Test Checklist

Unit

• Validate file type and size rules for video selection.
• Verify message payload creation for video media messages.
• Verify UI state transitions for upload/sending/error.

Integration

• Upload service integration returns media URL/metadata for videos.
• Chat flow sends video message and timeline receives/renders it.
• Error responses from upload/send are mapped to proper UI feedback.

E2E

• User uploads and sends a valid video in a room.
• Receiver sees the video message and can play it.
• Oversized/invalid video is blocked with clear feedback.

Notes

• Reuse existing image/media upload architecture where possible.
• Out of scope for this issue: video transcoding/compression pipeline changes.
• Confirm product limits (max size, allowed formats) before implementation.