Switch to generic cache control headers

[eyeseast]

Switches Cloudflare-CDN-Cache-Control to Cache-Control everywhere, since we only have one CDN now.

This will also allow browsers to cache pages, so we should watch for any staleness.

[github-actions]

Preview deployed: https://preview-1331.staging.documentcloud.org

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	58.57%	2380 / 4063
🔵	Statements	59.17%	2756 / 4657
🔵	Functions	60.52%	621 / 1026
🔵	Branches	59.34%	1460 / 2460

File Coverage

File	Stmts	Branches	Functions	Lines	Uncovered Lines
Changed Files
src/routes/(app)/add-ons/+layout.ts	0%	0%	0%	0%	5-18
src/routes/(app)/documents/+page.ts	0%	0%	0%	0%	7-40
src/routes/(app)/documents/[id]-[slug]/+page.ts	0%	0%	0%	0%	25-62
src/routes/(app)/projects/[id]-[slug]/+page.ts	0%	0%	0%	0%	17-70
src/routes/(pages)/about/+page.ts	0%	0%	0%	0%	6-25
src/routes/(pages)/help/[...path]/+page.ts	0%	0%	0%	0%	7-25
src/routes/(pages)/home/+page.server.ts	0%	0%	0%	0%	10-40
src/routes/embed/documents/[id]-[slug]/+page.ts	0%	0%	0%	0%	11-37
src/routes/embed/documents/[id]-[slug]/preview/+page.ts	0%	0%	0%	0%	12-38
src/routes/embed/documents/[id]/annotations/[note_id]/+page.ts	0%	0%	0%	0%	9-26
src/routes/embed/documents/[id]/annotations/[note_id]/preview/+page.ts	0%	0%	0%	0%	9-27
src/routes/embed/documents/[id]/pages/[page]/+page.ts	0%	0%	0%	0%	9-27
src/routes/embed/documents/[id]/pages/[page]/preview/+page.ts	0%	0%	0%	0%	8-24
src/routes/embed/projects/[project_id]-[slug]/+page.ts	0%	0%	0%	0%	10-61
src/routes/embed/projects/[project_id]-[slug]/preview/+page.ts	0%	0%	0%	0%	7-25

Generated in workflow #1215 for commit 4cd8c57 by the Vitest Coverage Report Action

[eyeseast]

Related research spike: https://github.com/MuckRock/research/tree/main/cloudflare-cache-analysis

It looks like the adapter uses the low-level cache API, but only for generic cache headers, not CF-specific.