[PM-22750] Reimplement fix old attachment logic

[shane-melton]

🎟️ Tracking

PM-22750

📔 Objective

Re-implement the missing fix attachment logic for old attachments without content encryption keys.

Also refactors the CipherAttachments and DownloadAttachment components to use Signals and OnPush change detection.

📸 Screenshots

Screen.Recording.2025-11-26.at.2.04.04.PM.mov

⏰ 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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Code Review in Progress

Review Checklist:

• Evaluate PR title and description
• Read all changed files
• Analyze fix old attachment logic implementation
• Review Angular Signal refactoring patterns
• Check security considerations (encryption, logging)
• Verify adherence to ADRs and coding standards
• Post comprehensive review feedback

[github-actions]

Checkmarx One – Scan Summary & Details – 5b278fe4-3aa3-4983-bd29-90096ba367e1

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