Add "My Phrases" functionality to Android, to match iOS behaviour

Describe the Enhancement
As a Vocable Android User, I want to be able to hit a "Star" button on the keyboard to save a custom phrase I just typed to a new category called "My Sayings". This category should only consist of phrases that I've saved using the "Star" button on the keyboard.

This functionality should match the iOS functionality shown below:

https://github.com/willowtreeapps/vocable-android/assets/73308097/571be943-bba8-4404-91ab-21f7a2b1b8b0

Acceptance Criteria
A user should be able to:

1. Navigate to Keyboard.
2. Type in a phrase.
3. Tap a Star button.
4. Navigate back to the "My Sayings" category and see the phrase they just starred.

Star Button
The Star button should have 3 states:

1. When no characters are typed into the keyboard: grayed out, un-filled, and disabled
2. When characters are typed into the keyboard: not-grayed-out, un-filled, and enabled
3. When the star is tapped in the enabled state: not-grayed-out, filled, and enabled

• When the star is tapped, it should stay filled until either the user changes the keyboard string or taps the star again.
• If the star is tapped and then un-tapped while the keyboard phrase stays the same, the current phrase should be added, and then removed, from the "My Sayings" category respectively

** My Sayings Category**

• Behaves exactly like a Preset category, except it can't be hidden ("Show Category" toggle is disabled), and it cannot be removed ("remove Category" button is disabled)

When in doubt, check out the iOS behaviour!