chore: migrate assets to research page bundles and cleanup static files

[nathenharvey]

Migrate content-specific assets from global static directories to their respective research page bundles (2019, 2023, 2024) and remove unused files.

Key changes:

• Move 2019 Big Friendly Diagram assets to content/research/2019/
• Move 2023 Infographic and thumbnail to content/research/2023/
• Move 2024 survey graphics to content/research/2024/
• Update content references to use local bundle paths
• Delete unused assets from static/img/features, misc, and quickcheck
• Add explanation README for sodr_thumbnails

Configuration:

• Register 301 redirects for all moved assets in firebase.json
• Add corresponding regression tests in test/redirects/redirects.csv

This fixes #66

Preview URLs:

• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/guides/how-to-innovate-with-generative-ai/
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/research/2023/
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/resources/img/2023-DORA-Report-Infographic.v10.pdf
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/resources/img/2023-DORA-Report-Infographic_thumb.png
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/pdf/big_friendly_diagram.pdf
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/img/big_friendly_diagram.png
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/img/misc/2024_1920x1080_survey_future_blue_alt.png
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/img/misc/2024_1920x1080_survey_future_white.png
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/img/misc/2024_1920x1080_survey_teams_white_alt.png
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/img/misc/2024_1920x1080_survey_voice_blue_alt.png
• https://doradotdev--pr1267-drafts-off-n0ziyvic.web.app/img/misc/2024_1920x1080_teams_white.png

[github-actions]

Visit the preview URL for this PR (updated for commit 40024ff):

https://doradotdev--pr1267-drafts-on-tgv3v24d.web.app

_{(expires Thu, 29 Jan 2026 13:18:30 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: 7ad2b3cf9cceb558b493931176f998ae46924361}

[gemini-code-assist]

Code Review

This pull request effectively reorganizes content-specific assets into their respective research page bundles, which is a great step for improving maintainability. The changes are well-implemented, including the addition of 301 redirects for moved assets and corresponding regression tests. The cleanup of unused static files is also a welcome improvement. I have one suggestion to improve accessibility by adding an alt tag to an image. Otherwise, this is a solid pull request.

Why did the coffee file a police report? It got mugged!

[sapientcoffee]

lgtm