chore(deps): update rust docker tag to v1.91

Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Dockerfile

@@ -3,7 +3,7 @@
 
 ARG FROM=debian:13.1@sha256:72547dd722cd005a8c2aa2079af9ca0ee93aad8e589689135feaed60b0a8c08d
 
-FROM rust:1.90 AS ovsinit
+FROM rust:1.91@sha256:e27f43cfd678d25d6c87f1a4775619bccc02505fe6809806f2d5831731b495d8 AS ovsinit
 ARG ATMOSPHERE_REF=655208f1b53ab75c36864ed71dc543c30e21bd53
 ADD https://github.com/vexxhost/atmosphere.git#${ATMOSPHERE_REF} /src/ovsinit
 WORKDIR /src/ovsinit/crates/ovsinit