Exclude storybook files from unit tests and ensure 100% unit test coverage

Unit test coverage has dropped from from 100% across the board to
```
------------------------------------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
------------------------------------|---------|----------|---------|---------|-------------------
All files | 82.12 | 96.5 | 90.62 | 80.78 |
```

This is mostly down to the `.stories.tsx` files being included for tests.

Adding the following lines to the `collectCoverageFrom` section in `packages/webui/jest.config.ts` will eliminate these:

```
'!./src/**/*.stories.{ts,tsx}',
'!**/*__mocks__*/**',
```

...however, coverage is still down and needs to be boosted back to 100%:

```
----------------------------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
----------------------------|---------|----------|---------|---------|-------------------
All files | 98.35 | 97.41 | 99.57 | 98.43 |
```