[FFS-4303] Make RegisterRoutes only wire HTTP paths to handlers.

[imhben]

Jira Ticket

• FFS-4303

Description

Moved all dependency creation out of router.go and into app.go. RegisterRoutes should not be a factory for dependencies and services but instead just for route composition.

Submitter Checklist

• Jira Ticket: The relevant Jira ticket is linked in the header.
• Evidence of Testing: I have included evidence of bench testing (e.g., terminal output, screenshots, logs) below.
• Security Boundary: I have checked if any security boundaries are changing.
  • If yes, I have pointed to the relevant Security Impact Analysis (SIA) or escalated to the security team.
• Backwards Compatibility: I have verified that these changes do not introduce any backwards compatibility issues.
  • [] If no, I have added appropriate new versions or feature flags and flagged the team and appropriate stakeholders
• I've updated the Confluence documentation, content in the /docs folder, and any API spec docs

Reviewer Checklist

• Verification: I have verified that the changes work as intended.
• Backwards Compatibility: I have confirmed that the code does not introduce any backwards compatibility issues.
• Security & Privacy: I have reviewed the changes for potential security or privacy risks (e.g., PII handling).
• Contract Compliance: If the public API contract changed, I have verified that it is reflected in api-spec/ and follows the organization's standards.
• Code Quality: The code is clean, well-tested, and follows the established patterns in the codebase.
• Code Quality: The code has unit and integration tests that cover relevant code changes.

Evidence of Testing

Paste test results here