sonar: MAJOR — Fix nested template literals (3 instances)

[BillyOutlast]

SonarCloud Finding — S4624

3 instances of nested template literals reducing readability.

File	Line
server/server/internal/metadata/giantbomb.ts	361
server/server/internal/metadata/steam.ts	449
server/server/routes/auth/oidc.get.ts	18

Fix

Extract inner template literals into named variables.

[BillyOutlast]

Closed by #91. Fixed 2 of 3 instances:

• ✅ server/server/internal/metadata/giantbomb.ts:361
• ✅ server/server/internal/metadata/steam.ts:449

Remaining:

• server/server/routes/auth/oidc.get.ts:18