Embed-aware Viewer links

[allanlasser]

Closes #724

• Refactors Viewer components into viewer directory
• Adds isEmbedded and getViewerHref utilities
• Generates Viewer hrefs based on mode, embed, and destination.

When you're using the Viewer on the document page, everything should work as before.

When you're using the Viewer on an embed route, you should stay within the embed view.

[github-actions[bot]]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	21.48%	6381 / 29696
🔵	Statements	21.48%	6381 / 29696
🔵	Functions	39.19%	136 / 347
🔵	Branches	57%	346 / 607

File Coverage

File	Stmts	% Branch	% Funcs	% Lines	Uncovered Lines
Changed Files
src/lib/components/documents/DocumentListItem.svelte	100%	71.42%	100%	100%
src/lib/components/embeds/DocumentEmbed.svelte	0%	0%	0%	0%	1-64
src/lib/components/forms/ConfirmRedaction.svelte	0%	0%	0%	0%	1-88
src/lib/components/layouts/DocumentLayout.svelte	0%	0%	0%	0%	1-117
src/lib/utils/viewer.ts	92.1%	100%	50%	92.1%	15-17

Generated in workflow #505

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