[PM-7317][Web] Clean up old components

[cyprain-okeke]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-7317

📔 Objective

When all marketing content has been changed to use the new Trial Initiation flow, we can remove the obsolete components:

TrialInitiationComponent

app-registration-form

Guard implemented in https://bitwarden.atlassian.net/browse/PM-7373

In addition, we should redirect /register to /signup.

📸 Screenshots

⏰ 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

[github-actions]

Checkmarx One – Scan Summary & Details – 63c0e7b2-7dff-4231-bd21-c56cfa942c59

Great job, no security vulnerabilities found in this Pull Request

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 34.86%. Comparing base (d820bfb) to head (90ccc30).

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...er/secrets-manager-trial-paid-stepper.component.ts	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12862      +/-   ##
==========================================
- Coverage   34.95%   34.86%   -0.09%     
==========================================
  Files        2977     2974       -3     
  Lines       90596    90373     -223     
  Branches    16980    16921      -59     
==========================================
- Hits        31671    31513     -158     
+ Misses      56468    56445      -23     
+ Partials     2457     2415      -42     

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[coroiu]

Approved platform changes