buf update breaks many things

[dmah42]

buf have changed the way their remote plugins work: https://buf.build/docs/migration-guides/migrate-remote-generation-alpha/

old versions of buf cannot download plugins (404) while new versions of buf cannot find plugins because they've moved.

the latter is somewhat solvable (WIP: #487) but the former isn't. things we need:

1. ensure a minimum version of buf (1.25.0 seems to work)
2. update all the plugin references in buf.gen.yaml (Migrate from buf's remote generation alpha #487)

[dmah42]

the newer plugin versions need tonic (and maybe other) updates in Cargo.toml. working on it.

[dmah42]

as part of 1 above, i added an explicit version check to the Makefile. this also means updating the docker images. i'm not completely happy about having a fixed version, but if buf is going to make breaking changes with minor version releases (and no config version bump) then i don't see an alternative to keep our builds reproducible.

[dmah42]

i think this is now resolved