[PM-27696] Revert feature flag removal for Chromium importers

[djsmith85]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-27697

📔 Objective

Reverting the removal of "pm-23982-chromium-importer" which got removed with #6415.

The feature flag was removed prematurely and the current Bitwarden desktop client (2025.10.0) still requires it to be served.

⏰ Reminders before review

• Contributor guidelines followed
• All formatters and local linters executed and passed
• Written new unit and / or integration tests where applicable
• Protected functional changes with optionality (feature flags)
• Used internationalization (i18n) for all UI strings
• CI builds passed
• Communicated to DevOps any deployment requirements
• Updated any necessary documentation (Confluence, contributing docs) or informed the documentation team

🦮 Reviewer guidelines

• 👍 (:+1:) or similar for great changes
• 📝 (:memo:) or ℹ️ (:information_source:) for notes or general info
• ❓ (:question:) for questions
• 🤔 (:thinking:) or 💭 (:thought_balloon:) for more open inquiry that's not quite a confirmed issue and could potentially benefit from discussion
• 🎨 (:art:) for suggestions / improvements
• ❌ (:x:) or ⚠️ (:warning:) for more significant problems or concerns needing attention
• 🌱 (:seedling:) or ♻️ (:recycle:) for future improvements or indications of technical debt
• ⛏ (:pick:) for minor or nitpick changes

[claude]

Claude encountered an error —— View job

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I'll analyze this and get back to you.

[github-actions]

Checkmarx One – Scan Summary & Details – 7d490cc3-3512-4261-85c7-41132d493ad0

Great job! No new security vulnerabilities introduced in this pull request

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.87%. Comparing base (e102a74) to head (cac448d).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6526      +/-   ##
==========================================
- Coverage   55.82%   51.87%   -3.95%     
==========================================
  Files        1905     1905              
  Lines       84210    84210              
  Branches     7510     7510              
==========================================
- Hits        47010    43687    -3323     
- Misses      35423    38821    +3398     
+ Partials     1777     1702      -75     

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