[WIP] message: Improve muted sender design.

[apoorvapendse]

Fixes: #32945.

CZO: #design > muted users

Screenshots and screen captures:

light	dark

In a mobile breakpoint we can hide the message and just have something like this:

I am doing this with cq_sm_min as the breakpoint for now.

light	dark

I hid the reveal label at the cq_mm_min breakpoint to avoid truncating "Muted user" on small screens and reduce visual clutter.
Feedback welcome.

Device: iPhone 12 Pro (390x844)

Without breakpoint	With breakpoint

Self-review checklist

• Self-reviewed the changes for clarity and maintainability
  (variable names, code reuse, readability, etc.).

Communicate decisions, questions, and potential concerns.

• Explains differences from previous plans (e.g., issue description).
• Highlights technical choices and bugs encountered.
• Calls out remaining decisions and concerns.
• Automated tests verify logic where appropriate.

Individual commits are ready for review (see commit discipline).

• Each commit is a coherent idea.
• Commit message(s) explain reasoning and motivation for changes.

Completed manual review and testing of the following:

• Visual appearance of the changes.
• Responsiveness and internationalization.
• Strings and tooltips.
• End-to-end functionality of buttons, interactions and flows.
• Corner cases, error conditions, and easily imagined bugs.

[apoorvapendse]

@whilstsomebody, can you do a buddy review if you find time?
Thanks.

[whilstsomebody]

Tag me again when this is ready for a review.

[apoorvapendse]

tagging @alya, @terpimost for a design review

[chrisbobbe]

How about "Muted user" in place of "Muted sender"? That's our plan in mobile; the fact that it's the sender is already communicated by the position of the text. (Thanks @sm-sayedi for mentioning this at zulip/zulip-flutter#1429 (comment) )