Fix accessibility issues arising from audit

[Floppy]

Fix anything that emerged from #1679

• Add password rules to signup page #2094
• "Skip to content" link #2095
• Add "lang" attributes for untranslated text that doesn't match the html lang #2096
• Fix tab ordering #2097
• Add text descriptions for problem icons to indicate severity #2098
• Blue warning icon has insufficient contrast #2099
• Add descriptive text to links that describe what will happen on click #2100
• Card metadata links are missing descriptive labels #2101
• Bulk edit table markup is no good for screenreaders #2102
• Pagination links aren't marked up as such #2103
• Group checkbox on upload page with its label #2104
• Can't reach 3d models via keyboard navigation #2105
• Image carousel should have controls to pause autorotation #2106
• Breadcrumb should be in nav tag not main #2107
• Account settings icon title text is unhelpful in screen reader #2108
• Change filter display from table to grid #2109
• Add a title to "Open" buttons that explains what they actually do #2111
• Bulk editor state icons look like interactive checkboxes but aren't #2112
• Column 2 (icon) on bulk file editor page does nothing #2113
• No descriptive text on bulk editor state icons #2114
• Bulk editor columns names don't appear in screen reader #2115
• Add skip links for large content blocks (models, creators, collections, tags) #2129

NLNet milestone 4.2

[Floppy]

Always more to do, but that's this list completed. 😅