upgrade ubuntu + sanitize packages

Linux/BaseBuilder/Dockerfile

@@ -1,23 +1,16 @@
-FROM ubuntu:24.04
+FROM ubuntu:26.04
 
 # Set timezone, noninteractive mode, and pipx path
 ENV TZ=Europe/Paris \
     DEBIAN_FRONTEND=noninteractive \
     PATH="/root/.local/bin:$PATH"
 
-# Use build cache for ccache
-RUN --mount=type=cache,target=/ccache
-
-# Dummy sudo (no security weakening)
 RUN echo '#!/bin/bash\n$@' > /usr/bin/sudo \
     && chmod +x /usr/bin/sudo
 
-# Install base dependencies in one layer
 RUN apt-get update && apt-get install -y \
         unzip \
         curl \
         wget \
-        lsb-release \
-        software-properties-common \
-        gnupg \
-        python3
+        python3 \
+        pipx