compose: Remove denominator in character counter

[ankitsuryawanshi9892]

Previously when a message is close to or above the character limit, character counter is displayed in this format: text_length/max_length. This PR removes the denominator and display the number of characters remaining or the number of characters over the limit. Also tooltip is added to help users understand why the send button is disabled. This PR solves the issue #28706

Fixes: #28706

Screenshots and screen captures:

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.

[N-Shar-ma]

@ankitsuryawanshi9892 Are you still working on this? You 1st need to lint your code with the command described in the error message.

[ankitsuryawanshi9892]

@N-Shar-ma Yes I am working on this, backend tests are failing...