UI/UX: Styling: Update buttons' color

Update the colors of the following buttons:
#### Main screen:
- [x] [Apply] button's enabled-state: change border & fill color from grey #414851 (named "Foreground" in the default color palette) to blue #007ACC (named "Current") with hover border & fill color #41B3FF - to emphasize it

#### Curation - start screen:
- [x] [Start] button's enabled-state: change border & fill color from grey #414851 (named "Foreground") to blue #007ACC (named "Current") with hover border & fill color #41B3FF - to emphasize it

#### Curation - main screen:
- [x] [Save Curation CSV] button's enabled-state: change fill color from blue #007ACC (named "Current" in the default color palette) to grey #414851 (named "Foreground") - to de-emphasize it
- [x] All disabled buttons should have same disabled colors (also it looks like we have a couple disable button styles here that should be the same and consistent): border & fill color #414851 ("Foreground"), text fill color #6A7380. Their enabled colors stay the same respectively.
This applies to the [+Create], [Delete] and [Save] buttons in the screenshot below.
Current____
Expected __

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## Stretch
Update section border color from currently #AAAAAA to #414851 ("Foreground"). These section border appear in:
- [x] Curation - main screen: (1) the progress bar section, (2) section of "Use this image for training..."

- [x] Training: training images section

- [x] Prediction: input image(s) section