refactor: narrow api route dependency surfaces

[lan17]

Summary

• narrow API route dependencies from broad Application typing to route-specific protocol surfaces
• move auth, mode, and database guards onto smaller protocol-based app dependencies
• add focused dependency tests for minimal protocol-shaped app objects

Testing

• TEST_DB_DSN=postgresql://homesec:homesec@localhost:5432/homesec_api_deps_ci make check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.84%. Comparing base (298a5c5) to head (eaaa9a0).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #50      +/-   ##
==========================================
+ Coverage   83.73%   83.84%   +0.10%     
==========================================
  Files         110      110              
  Lines        9814     9858      +44     
==========================================
+ Hits         8218     8265      +47     
+ Misses       1596     1593       -3     

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[lan17]

Closing this as a deliberate discard. The refactor was technically clean and validated, but after review it adds protocol/wrapper ceremony without enough maintainability payoff. We'll revisit API dependency narrowing only when it removes real route complexity or supports a broader API refactor.