admin: add baseConfig option

[yottahmd]

This PR is related to #216

[codecov-commenter]

Codecov Report

Merging #245 (ff88a2a) into main (dac81b6) will increase coverage by 0.41%.
The diff coverage is 96.22%.

@@            Coverage Diff             @@
##             main     #245      +/-   ##
==========================================
+ Coverage   86.31%   86.73%   +0.41%     
==========================================
  Files          46       46              
  Lines        3282     3287       +5     
==========================================
+ Hits         2833     2851      +18     
+ Misses        322      311      -11     
+ Partials      127      125       -2     

Impacted Files	Coverage Δ
internal/admin/loader.go	95.52% <93.33%> (+12.18%)	⬆️
cmd/dagu.go	75.00% <100.00%> (+2.08%)	⬆️
cmd/dry.go	77.77% <100.00%> (-2.87%)	⬇️
cmd/retry.go	86.04% <100.00%> (-0.92%)	⬇️
cmd/start.go	79.31% <100.00%> (-1.94%)	⬇️
cmd/status.go	70.00% <100.00%> (-5.00%)	⬇️
cmd/stop.go	78.57% <100.00%> (-4.77%)	⬇️
internal/admin/config.go	85.21% <100.00%> (+0.95%)	⬆️
internal/config/loader.go	83.67% <100.00%> (-2.14%)	⬇️
internal/controller/controller.go	75.97% <100.00%> (-0.27%)	⬇️
... and 5 more

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