feat: share checklists as simple text

[naveensingh]

Type of change(s)

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

What changed and why

Modified the share functionality to share plan checklists as plain text. In-app sorting is respected in the final text.

Tests performed

• Tested sharing checklists with all sorting options

Before & after preview

Items are shared in the following format:

[x] Timothy hay
[x] Pellets
[ ] Low-pile carpets
[x] Bananas

Closes the following issue(s)

• Closes Share checklists as simple text #96

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.