Feature request: Select and copy multiple messages at once in the mobile app

[pradelgorithm]

Is your feature request related to a problem? Please describe.

Yes. In the Chatwoot mobile app, agents currently have to copy messages one by one when they need to reuse or share several messages from the same conversation. This is slow and frustrating, especially when handling long customer conversations on a phone.

Other messaging apps such as WhatsApp and Telegram allow users to long-press a message, enter selection mode, select multiple messages, and then perform an action on all of them together.

Describe the solution you'd like

Add multi-message selection in the mobile conversation view.

Suggested interaction:

1. Long-press any message to enter selection mode.
2. Tap additional messages to select or deselect them.
3. Show the number of selected messages in the header.
4. Provide a Copy action that copies all selected messages to the clipboard in chronological order.
5. Preserve readable separation between messages, ideally including sender and timestamp where appropriate.
6. Provide a clear cancel action to exit selection mode.

Expected benefit

• Faster handling of customer conversations on mobile.
• Easier sharing of conversation excerpts with teammates or other tools.
• Less repetitive work for agents.
• A mobile experience consistent with common messaging applications.

Acceptance criteria

• Agents can select more than one message within a conversation.
• Selected messages are visually highlighted.
• Tapping Copy copies all selected messages in chronological order.
• The feature works for both incoming and outgoing text messages.
• Selection mode can be cancelled without changing the conversation.
• The behavior is supported on both Android and iOS.

Related issue

Related to chatwoot/chatwoot#11487, which mentions selecting multiple messages while forwarding, but this request is specifically for multi-selection and copying within the Chatwoot mobile app.