fix(docker): use ubuntu:24.04 base image for all runtime Dockerfiles

Resolves GLIBC_2.39 mismatch error — CI builds on ubuntu-latest
(24.04) which links against glibc 2.39, but debian:bookworm-slim
only provides glibc 2.36, causing binary execution failure.

docker/adminrpc.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates libssl3 \

docker/app.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates libssl3 git \

docker/email-worker.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates libssl3 procps \

docker/git-hook.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates libssl3 openssh-client procps git \

docker/gitserver.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates libssl3 openssh-server git \

docker/operator.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates git \

docker/static.Dockerfile

@@ -1,5 +1,5 @@
 # Runtime only — binary built externally via cargo
-FROM debian:bookworm-slim
+FROM ubuntu:24.04
 
 RUN apt-get update && apt-get install -y --no-install-recommends \
     ca-certificates git \