This reverts commit 20baa2c.

### Why is this Change Important & Necessary?
Closes #12668 

#12564 Improved the layout of the calendar, and also attempted to
improve accessibility on different browsers. It was failing CSS lint
since many of the rules were legacy.

### What is the New Behavior?
Removed rules, but left functionality the same. If there is still an
issue on specific browsers, we should make a new issue to adjust it
specifically.

### What steps should a reviewer take to reproduce or test the bug or
new feature?
Calendar has fixed column widths and is responsive.

### Automated Testing & Documentation
N / A

### Other information
Not a breaking change.

Fixes Submitty#12519 

**Description:**
This pull request addresses a UI rendering bug in the Calendar component
specifically using Safari. By refactoring the component's layout to use
flexbox and removing rigid CSS hardcoded constraints, we ensure a
consistent and responsive experience across all modern browsers and
screen sizes.

### Why is this Change Important & Necessary?
This change is necessary to fix a visual bug where the year selection
dropdown was being cropped on safari. The root cause was an hardcoded
width on the select element that prevented the container from expanding
to fit the text. By switching to a dynamic width and a flexbox based
layout, we ensure that the calendar remains functional and visually
correct on all platforms.

### What is the New Behavior?
- Bug fix: the year selection component no longer appears cropped on
safari.
- Flexbox refactor: the structure of the <thead> element of the table
has been migrated to flexbox. This prevents element collapse and ensures
the central column (containing the month and year) scales correctly
based on its children's dimensions.
- Improved Responsiveness: the new layout is more robust across
different screen sizes while maintaining the original design aesthetic.
- Cross-Browser Standards: added css prefixers to ensure the flexbox and
other properties and UI elements are interpreted consistently by chrome,
firefox, and safari.

### What steps should a reviewer take to reproduce or test the bug or
new feature?
1. Open the application using safari.
2. Navigate to the calendar component and observe the year selector at
the top.
3. Verify that the year is fully visible and not cut off.
4. Resize the browser window to ensure the flexbox layout adapts without
elements overlapping or collapsing.
5. Perform the same checks in chrome and firefox to ensure no
regressions were introduced.

### Automated Testing & Documentation
This PR focuses on css layout and html structure. Manual visual testing
was performed across major browsers (Chrome, Safari, Firefox) to confirm
the fix and layout stability. No changes were made to the underlying
JavaScript logic, so existing functional tests should remain unaffected.

### Other information
- Is this a breaking change? No.
- Does this PR include migrations to update existing installations? No.
- Are there security concerns with this PR? No.

### Before

https://github.com/user-attachments/assets/784a7a98-3077-4f9e-af67-3553a241d4ad

### After
<img width="1582" height="1030" alt="image"
src="https://github.com/user-attachments/assets/234efabf-0ddf-4ab1-874d-a2d261489247"
/>


https://github.com/user-attachments/assets/b75dc296-a639-406f-9d2c-40a401d8902f

---------

Co-authored-by: Justin Manion <[email protected]>

Fixes Submitty#12519 

**Description:**
This pull request addresses a UI rendering bug in the Calendar component
specifically using Safari. By refactoring the component's layout to use
flexbox and removing rigid CSS hardcoded constraints, we ensure a
consistent and responsive experience across all modern browsers and
screen sizes.

### Why is this Change Important & Necessary?
This change is necessary to fix a visual bug where the year selection
dropdown was being cropped on safari. The root cause was an hardcoded
width on the select element that prevented the container from expanding
to fit the text. By switching to a dynamic width and a flexbox based
layout, we ensure that the calendar remains functional and visually
correct on all platforms.

### What is the New Behavior?
- Bug fix: the year selection component no longer appears cropped on
safari.
- Flexbox refactor: the structure of the <thead> element of the table
has been migrated to flexbox. This prevents element collapse and ensures
the central column (containing the month and year) scales correctly
based on its children's dimensions.
- Improved Responsiveness: the new layout is more robust across
different screen sizes while maintaining the original design aesthetic.
- Cross-Browser Standards: added css prefixers to ensure the flexbox and
other properties and UI elements are interpreted consistently by chrome,
firefox, and safari.

### What steps should a reviewer take to reproduce or test the bug or
new feature?
1. Open the application using safari.
2. Navigate to the calendar component and observe the year selector at
the top.
3. Verify that the year is fully visible and not cut off.
4. Resize the browser window to ensure the flexbox layout adapts without
elements overlapping or collapsing.
5. Perform the same checks in chrome and firefox to ensure no
regressions were introduced.

### Automated Testing & Documentation
This PR focuses on css layout and html structure. Manual visual testing
was performed across major browsers (Chrome, Safari, Firefox) to confirm
the fix and layout stability. No changes were made to the underlying
JavaScript logic, so existing functional tests should remain unaffected.

### Other information
- Is this a breaking change? No.
- Does this PR include migrations to update existing installations? No.
- Are there security concerns with this PR? No.

### Before

https://github.com/user-attachments/assets/784a7a98-3077-4f9e-af67-3553a241d4ad

### After
<img width="1582" height="1030" alt="image"
src="https://github.com/user-attachments/assets/234efabf-0ddf-4ab1-874d-a2d261489247"
/>


https://github.com/user-attachments/assets/b75dc296-a639-406f-9d2c-40a401d8902f

---------

Co-authored-by: Justin Manion <[email protected]>

### Why is this Change Important & Necessary?
Closes Submitty#12668 

Submitty#12564 Improved the layout of the calendar, and also attempted to
improve accessibility on different browsers. It was failing CSS lint
since many of the rules were legacy.

### What is the New Behavior?
Removed rules, but left functionality the same. If there is still an
issue on specific browsers, we should make a new issue to adjust it
specifically.

### What steps should a reviewer take to reproduce or test the bug or
new feature?
Calendar has fixed column widths and is responsive.

### Automated Testing & Documentation
N / A

### Other information
Not a breaking change.