- Update Dockerfile to use golang:1.25-alpine to match go.mod (go 1.25.7)
- Optimize logger by avoiding string concatenation in file writes
- Add explicit empty string assignment for fieldStr when no fields
These changes improve build consistency and reduce memory allocations
in the hot logging path, which is important for the project's goal
of running on resource-constrained devices (<10MB RAM).
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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