Fix media DB possibly leaking connections

[S7evinK]

Grafana Pyroscope unveiled that we are hitting https://github.com/golang/go/blob/ad10fbd3c4ec7413775028213f4d5089b18926f7/src/database/sql/sql.go#L2739-L2742 for media DB queries.

Making the methods pointer receivers fixes this.

(Also some minor error cosmetic updates)

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 67.52%. Comparing base (46902e5) to head (6f5ab8f).

Files	Patch %	Lines
mediaapi/storage/shared/mediaapi.go	66.66%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3372      +/-   ##
==========================================
+ Coverage   67.51%   67.52%   +0.01%     
==========================================
  Files         521      521              
  Lines       47366    47362       -4     
==========================================
+ Hits        31977    31982       +5     
+ Misses      11405    11394      -11     
- Partials     3984     3986       +2     

Flag	Coverage Δ
unittests	52.76% <66.66%> (+<0.01%)	⬆️

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[devonh]

Seems weird that it ever wasn't pointer receivers 🤷
Looks good!