docs: improve Docker Hub README clarity and consistency

[SebConejo]

Summary

• Replace "setup wizard" language with "sign up" + "first account becomes admin" to match manifest.build/docs
• Break the review-before-running section into separate copyable commands inside a collapsible <details> card
• Make Option 2 (Docker Compose) and Option 3 (Docker Run) more explicit about what the user should actually do
• Add "Give it about 30 seconds to boot" note (matches docs)
• Replace "TypeORM migrations" with "database migrations" (users don't need to know the ORM)

Test plan

• Verify Markdown renders correctly on GitHub (collapsible card, code blocks, tables)
• Spot-check that all install commands match the actual files in docker/

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Summary by cubic

Improve the Docker Hub README for clarity and consistency with manifest.build/docs. Switch “setup wizard” to “sign up” (first account is admin), add a 30s boot note, turn the review-before-running flow into copyable steps inside a collapsible card, make Docker Compose/Run steps explicit, replace “TypeORM migrations” with “database migrations,” and tighten up tables and wording.

^{Written for commit c8e8f34. Summary will update on new commits.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.94%. Comparing base (158cbaf) to head (c8e8f34).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1568   +/-   ##
=======================================
  Coverage   97.94%   97.94%           
=======================================
  Files         118      118           
  Lines        8616     8616           
  Branches     3242     3242           
=======================================
  Hits         8439     8439           
  Misses        175      175           
  Partials        2        2           

Flag	Coverage Δ
frontend	97.93% <ø> (ø)
shared	100.00% <ø> (ø)

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[cubic-dev-ai]

No issues found across 1 file