Create v10.4 Release Post & Update post-release docs

[EngincanV]

Description

Resolves https://github.com/volosoft/vs-internal/issues/8474#issuecomment-4343434770

Blog post url will be https://abp.io/community/announcements/announcing-abp-10-4-release-candidate-7ukyudm0

If you have screenshots from the MudBlazor theme with ABP, can you add it to the relevant section in the blog post, before merging please? @maliming

Checklist

• I fully tested it as developer / designer and created unit / integration tests
• I documented it (or no need to document or I will create a separate documentation issue)

[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 80.9%, saving 2.6 MB.

Filename	Before	After	Improvement	Visual comparison
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/cover-image.png	2.5 MB	456.6 KB	82.2%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/login-via-email.png	273.0 KB	66.5 KB	75.6%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/login-via-email2.png	237.5 KB	55.4 KB	76.7%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/account-settings.png	223.5 KB	48.8 KB	78.2%	View diff

1 image did not require optimisation.

[Copilot]

Pull request overview

Adds ABP v10.4 RC release communication and post-release documentation updates, primarily by introducing the v10.4 migration guide and a corresponding blog post with screenshots.

Changes:

• Added the ABP v10.4 migration guide and linked it from the migration guides index.
• Added the ABP Platform 10.4 RC blog post and related screenshots/assets.

Reviewed changes

Copilot reviewed 3 out of 8 changed files in this pull request and generated 2 comments.

File	Description
docs/en/release-info/migration-guides/index.md	Adds the 10.4 migration guide entry to the migration guides list.
docs/en/release-info/migration-guides/abp-10-4.md	New migration guide documenting key v10.4 behavior/dependency changes (URL-based localization, 2FA token semantics, MudBlazor, etc.).
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/POST.md	New v10.4 RC announcement post describing major features and changes.
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/studio-switch-to-preview.png	Adds a screenshot referenced by the blog post.

[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 12.6%, saving 15.4 KB.

Filename	Before	After	Improvement	Visual comparison
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/login-via-email.png	66.5 KB	58.0 KB	12.8%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/login-via-email2.png	55.4 KB	48.5 KB	12.4%	View diff

3 images did not require optimisation.

[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 77.4%, saving 1.2 MB.

Filename	Before	After	Improvement	Visual comparison
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/mud-index.png	969.5 KB	235.2 KB	75.7%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/mud-identity.png	349.4 KB	67.9 KB	80.6%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/mud-studio.png	217.5 KB	44.0 KB	79.8%	View diff

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[github-actions]

Images automagically compressed by Calibre's image-actions ✨

Compression reduced images by 73.8%, saving 822.6 KB.

Filename	Before	After	Improvement	Visual comparison
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/mud-index.png	824.3 KB	224.6 KB	72.7%	View diff
docs/en/Blog-Posts/2026-04-29 v10_4_Preview/mud-identity.png	290.1 KB	67.1 KB	76.9%	View diff

6 images did not require optimisation.