[WIP] Enhance: Main container

[sprocketc]

Note for reviewers: This enhancement (along with #9846 & #9880), is changing the way we use elevation backgrounds. Although the enhancements should work on both theme modes, you are advised to mainly test this on our default dark theme. The problem with our light theme is that the shade of the elevated backgrounds should be inverted. The higher we you go, the lighter the background should be (see our color-level css class). We are going to make this change on a theme related PR. It would also be nice if we could release the right/left/center enhancements together, because they are all part of the same concept.

• Handle elevation background. Using the color-level class should ensure that nested elevated blocks will be properly rendered.
• Move page actions from header dropdown to a dedicated menu next to the page title (this one is the reason I added [minor change] to the title). This decision might be questionable when we view single pages on mobile, because we need the space, and two similar "dots" button will be close to each other. We can make adjustments later on. We can also add dedicated buttons for "favorite" or other actions next to our dots menu.
• Enhance journals route. Each day should look like an individual pane with its own dropdown. Also changed the way the height of the first day behaves.
• Add page menus to whiteboard cards on dashboard
• Minor adjustments on "all pages" route (sticky header)

[Bad3r]

With everything now in 'cards' (?), it makes it easier to notice the misalignment of UI elements.

I attempted to create a grid screenshot to help explain:

1. The horizontal space between the left window edge and the journal tab is larger than the space between the right window edge and the contents tab in the right sidebar.

2. The vertical spacing between journal cards, left sidebar cards, and right sidebar cards differ, making the UI feel more complex or overwhelming.

3. The buttons at the top of the right sidebar (contents, page graph, help) have minimal spacing between them compared to other buttons like the arrow back and arrow forward in the top bar.

4. the space from the top window border and the journal date (Aug 5th, 2023) feels too large compared to the space at the top of the left sidebar and right sidebar

[Bad3r]

Note that this change makes viewing the content in the right sidebar challenging.

The spacing from the right and left do not match and there is too much whitespace at the top:

[sprocketc]

Note that this change makes viewing the content in the right sidebar challenging.

That's a valid issue that I missed. Please hold this until it's resolved.

[hillsmao]

I beg you to stop this crazy idea