chore(deps): update golang:1.25.5-alpine docker digest to ac09a5f

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
golang	stage	digest	7256733 -> ac09a5f

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Configuration

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[github-actions]

➡️ Go test coverage stayed the same at 9.7% compared to 83f3c4b

⚠️ 5 of 6 packages have zero coverage.

• github.com/Depado/smallblog
• github.com/Depado/smallblog/cmd
• github.com/Depado/smallblog/domain
• github.com/Depado/smallblog/filesystem
• github.com/Depado/smallblog/router

No change in coverage for any package.

View coverage for all packages

# Package Name                           | Coverage
- github.com/Depado/smallblog            |     0.0%
- github.com/Depado/smallblog/cmd        |     0.0%
- github.com/Depado/smallblog/domain     |     0.0%
- github.com/Depado/smallblog/filesystem |     0.0%
+ github.com/Depado/smallblog/models     |    23.7%
- github.com/Depado/smallblog/router     |     0.0%