feat: always show pin/unpin as action

[naveensingh]

Type of change(s)

• Bug fix
• Feature / enhancement
• Infrastructure / tooling (CI, build, deps, tests)
• Documentation

What changed and why

• Added unpin icon and updated the pin icon.
• Updated the unpin condition to only show when all selected items are already pinned. Previously, both pin and unpin options showed up when selecting both pinned and unpinned conversations.
• Update the menu layout to always show pin/unpin as action buttons.

Tests performed

• Pinning/unpinning convos

Closes the following issue(s)

• Not tracked. It's ok to bend the rules sometimes.

Checklist

• I read the contribution guidelines.
• I manually tested my changes on device/emulator (if applicable).
• I updated the "Unreleased" section in CHANGELOG.md (if applicable).
• I have self-reviewed my pull request (no typos, formatting errors, etc.).
• All checks are passing.