Summary

The first post-merge run of the new Build and publish image workflow failed with:

#31 [linux/amd64 build 5/5] RUN make go-generate build ENABLE_VIPS=true
#31 0.093 go: ../go.mod requires go >= 1.25.0 (running go 1.24.13; GOTOOLCHAIN=local)
#31 0.094 make: *** [../.make/go.mk:102: bin/opencloud] Error 1
ERROR: failed to build: failed to solve: process "/bin/sh -c make go-generate build ENABLE_VIPS=true" did not complete successfully: exit code: 2

Root cause: go.mod declares go 1.25.0 (in line with upstream), but the build stage of Dockerfile is pinned to golang:1.24-alpine. Alpine's golang image defaults to GOTOOLCHAIN=local, so the toolchain does not auto-download the required version and the build hard-fails.

This PR bumps the build base from golang:1.24-alpine to golang:1.25-alpine to match the declared minimum. Single-line change.

Review & Testing Checklist for Human

Green-risk; one item:

• Confirm the docker workflow goes green for both linux/amd64 and linux/arm64 after this lands on main. The workflow runs automatically on push, so no manual step is needed.

Notes

• Upstream opencloud-eu/opencloud:main has the same out-of-sync Dockerfile, but upstream's CI runs on Woodpecker, not on this Dockerfile, so they don't see the failure. Worth a courtesy PR upstream if you'd like — happy to send one.
• This does not change anything about the runtime image (alpine:3.23 + ffmpeg + vips), so the deploy guide in DEPLOYMENT.md and the video-thumbnail feature both remain unchanged.

Link to Devin session: https://app.devin.ai/sessions/620d4cc7fd8b46a386213618cd65b662