fix: widgets customization (#201)

[Aga-C]

Type of change(s)

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

What changed and why

• Fixed changing colors and transparency if there are multiple widgets on the screen.
• Existing code was explicitly implying, that change can only be done if there's just one widget created.
• Because widget colors are stored in DB (so each one can have different colors), I've added a function to update all widget colors in DB.

Before & after preview

qemu-system-x86_64_Wj0K8pAJPO.mp4

qemu-system-x86_64_0ij4AoukVL.mp4

Closes the following issue(s)

• Closes Widget transparency can't be changed within the app #201

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).
• All checks are passing.

[naveensingh]

Thanks