Rendering discrepancies on web interfaces between latest (2.0.2) and current develop branch

[zenmonkeykstop]

Issue collecting rendering changes coming from the a11y refactor that probably need to be tweaked:

• Superfluous top padding on Source Interface (SI) flash messages #6081
• SI Javascript security level instruction dialog is overwritten by header text and not clickable #6082
• SI "Yes, delete all replies" button is now 3 lines of text instead of 2, increasing overall height #6083
• Journalist Interface All Sources page is missing gray border on right panel, padding between left and right panels #6084
• /lookup: missing highlight on "You have received a reply..." #6093

(if you see something else please add it above!)

[cfm]

Draft pull request #6096 can serve as the accumulator for these fixes, so that we can easily review and merge the full set, including for any further discrepancies we may notice, in one fell swoop.