Add support for multiple product releases

[ryanwhitney]

Description

Fixes #1205.

• Adds support for releases of multiple SecureDrop products, which editors can manage on their own
  • Adds new product snippet that release snippets FK to
    • release snippets are automatically associated to a product if there is an existing product with matching repo_full_name (i.e. freedomofpress/securedrop) when the webhook is fired
• Adds a replay_release_webhook management command for testing webhooks locally
• Frontend updates to show multiple releases
  • • some template and sass cleanup along the way
• Removes documentation links per request, as individual docs are to be combined into the main nav docs link

Includes both database and data migrations:

• 0002: adds the new product model
• 0003: creates a SecureDrop product snippet and backfills existing releases with it

After this PR, we'll need to:

• Add new products
• Add webhooks to the corresponding repos
• Watch the next SD releases and ensure everything looks good
• After there's multiple releases:
  • Update page.release_title on /news to be plural ("Current releases")

Type of change

• Bug fix
• New feature
• Vulnerabilities update
• Config changes
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires an admin update after deploy
• Includes a database migration removing or renaming a field

Testing

I think the easiest way to test this is to use the new management command, which can be deleted afterwards if no longer needed:

docker compose exec django ./manage.py replay_release_webhook \
      --repo freedomofpress/securedrop-inbox \
      --tag 1.0.0 \
      --release-url https://github.com/freedomofpress/securedrop-inbox/releases/tag/1.0.0 \
      --published-at 2026-05-29T12:00:00Z

Testing:

1. Ensure the original SecureDrop product is still showing after running the migrations
2. Run a replay_release_webhook command with a new repo like freedomofpress/securedrop-inbox

• Should run but no release should be created

3. Add a new product snippet for freedomofpress/securedrop-inbox
4. Run the command again

• You should now see a new matching release snippet
• The new product release should now be showing on the homepage and /news page

5. Create blog posts for the new releases and ensure the release notes links show on the homepage and /news page

Post-deployment actions

In case this PR needs any admin changes or run a management command after deployment, mention it here:

Checklist

General checks

• Linting and tests pass locally
• The website and the changes are functional in Tor Browser
• There is no conflicting migrations
• Any CSP related changes required has been updated (check at least both firefox & chrome)
• The changes are accessible using keyboard and screenreader

If you made changes to directory listing:

• Verify directory filters (country/topic/language) work as expected
• Verify directory search works as expected

If you made changes to contact form

• Verify contact form submissions works as expected
• Verify if any CSP changes required (test at least both firefox & chrome)

If you made changes to scanner

• Verify that the directory scan result page in admin interface loads as expected
• Verify that the API at /api/v1/directory returns directory entries and scan results as expected

If it's a major change

• Do the changes need to be tested in a separate staging instance?

If you made any frontend change

If the PR involves some visual changes in the frontend, it is recommended to add a screenshot of the new visual.