Simplify FIB atlas registration workflow

[tieneupin]

Removes the try-except blocks in the workflow and lets the parent feedback_callback function handle any raised exceptions and database connection closures. Switches to using the register_dcg function introduced in PR #901 instead of loading the whole entry point.

[codecov]

Codecov Report

❌ Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.16%. Comparing base (ae7931a) to head (f84c22a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #903      +/-   ##
==========================================
+ Coverage   55.12%   55.16%   +0.04%     
==========================================
  Files         103      103              
  Lines       11559    11532      -27     
  Branches     1533     1533              
==========================================
- Hits         6372     6362      -10     
+ Misses       4843     4826      -17     
  Partials      344      344              

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