perf(db): optimize N+1 query in comment list

[qwqcode]

QPS increased by 46%
Latency reduced by 29%

The test case is the first page of the official website's comment data pagination, SQLITE database (caching is turned off).

[codecov]

Codecov Report

Attention: Patch coverage is 52.45902% with 29 lines in your changes are missing coverage. Please review.

Project coverage is 34.83%. Comparing base (44bca8d) to head (12a432b).

Files	Patch %	Lines
internal/dao/migrate.go	38.70%	19 Missing ⚠️
server/handler/comment_list.go	0.00%	4 Missing ⚠️
internal/dao/cook.go	84.61%	2 Missing ⚠️
server/handler/comment_create.go	0.00%	2 Missing ⚠️
server/handler/stat.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #799      +/-   ##
==========================================
+ Coverage   34.60%   34.83%   +0.23%     
==========================================
  Files         117      117              
  Lines        4757     4805      +48     
==========================================
+ Hits         1646     1674      +28     
- Misses       3004     3024      +20     
  Partials      107      107              

Flag	Coverage Δ
go	34.83% <52.45%> (+0.23%)	⬆️

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