fix: override sticky positioning issues caused by Bootstrap

[TanCodeX]

What does this PR do?

This PR resolves layout issues caused by position: sticky styles inherited from Bootstrap. Sticky elements were undesirably fixed to the viewport during scroll, disrupting the user experience.

Fixes #1276

Changes Made:

• .App-header
  -- Changed position: sticky to position: relative
  -- Removed top: 0.3rem
  -- Used !important to override Bootstrap

• .i4k-symbols-list dl
  -- Changed position: sticky to position: relative
  -- Removed top: 0
  -- Used !important to override Bootstrap

These changes ensure:

• Elements do not stick to the viewport while scrolling
• Natural flow of elements is preserved
• Visual consistency is maintained

The updated styles have been added to style.css, which is already loaded after Bootstrap, ensuring our rules take effect due to !important.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Chore (refactoring code, technical debt, workflow improvements)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How should this be tested?

• Run the app
• Scroll through the page
• Confirm that .App-header and .i4k-symbols-list dl no longer stick to the viewport
• Verify that layout and scroll behavior remain visually consistent

Checklist

• I have read the contributing guide
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas (N/A for CSS fix)
• I have checked if my PR needs changes to the documentation (N/A)
• I have checked that my changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works (N/A for CSS)
• I have checked that new and existing unit tests pass locally with my changes

[KernelDeimos]

Are there any changes made to style.css? If there are the formatting needs to be removed so we can review it (the file is very large so it's easy to miss something when most lines are considered changes). Also let us know the visual impact, i.e. a specific issue a user might experience from a non-technical pov that's solved by fixing bootstrap position overrides.

[TanCodeX]

Yes, there are changes made to style.css, specifically to override Bootstrap’s position: sticky behavior on .App-header and .i4k-symbols-list dl. We’ll remove any unnecessary formatting or whitespace changes to minimize diff noise and make the review easier - thanks for flagging that.
Visual Impack :
Previously, headers and symbol lists would remain stuck to the top of the screen while scrolling, which could feel unnatural or obstruct content below. After this change, those elements now scroll normally with the rest of the page, resulting in a smoother and more expected user experience, especially on long pages.

[KernelDeimos]

I'd like a concrete example of this issue, like a specific area in Puter's UI that's affected. I closed the issue that was referenced - #1276 - because it appeared to be relating to a specific app in Puter rather than Puter's UI itself, and apps should not be able to be affected by Puter's CSS because they run in iframes.