Run `go fix ./...` and keep mechanical modernization updates.
- Replace `interface{}` with `any` in signatures and local types
- Apply formatter/style cleanups from go1.26 tooling
- Keep `omitempty` behavior-preserving simplifications suggested by fix
- No functional feature changes intended
Validation:
- go test ./... -run '^$' -count=1 (Go 1.26.0)
- GOTOOLCHAIN=go1.24.10 go test ./... -run '^$' -count=1
Signed-off-by: Michael Mayer <michael@photoprism.app>
