feat(server): add env var to specify account database

[rot1024]

Overview

What I've done

Add an env var (REEARTH_DB_ACCOUNT) to specify the database name for accounts, separate from the regular database

What I haven't done

How I tested

Which point I want you to review particularly

Memo

[netlify]

✅ Deploy Preview for reearth-web canceled.

Name	Link
🔨 Latest commit	8276aab
🔍 Latest deploy log	https://app.netlify.com/sites/reearth-web/deploys/64e6e0096946a9000a665d78

[codecov]

Codecov Report

Merging #640 (8276aab) into main (0ef6a88) will decrease coverage by 0.01%.
The diff coverage is 32.14%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #640      +/-   ##
==========================================
- Coverage   27.91%   27.91%   -0.01%     
==========================================
  Files        1459     1459              
  Lines      158959   158958       -1     
  Branches     3737     3737              
==========================================
- Hits        44378    44373       -5     
- Misses     113491   113497       +6     
+ Partials     1090     1088       -2     

Flag	Coverage Δ
server	35.22% <32.14%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
server/internal/app/config/config.go	43.85% <ø> (ø)
server/internal/app/repo.go	0.00% <0.00%> (ø)
server/internal/infrastructure/mongo/container.go	0.00% <0.00%> (ø)
server/internal/usecase/interactor/dataset.go	0.00% <ø> (ø)
server/internal/usecase/interactor/layer.go	3.51% <ø> (ø)
server/internal/usecase/repo/container.go	37.75% <0.00%> (-2.91%)	⬇️
server/e2e/common.go	67.96% <100.00%> (+2.74%)	⬆️