chore(image): bump caido-cli v0.48.0 → v0.56.0; parametrize via CAIDO_VERSION

The pinned URL pattern (https://caido.download/releases/v<X>/caido-cli-v<X>-linux-<arch>.tar.gz)
is canonical — it's published by api.caido.io/releases/latest. HEAD requests
return 404 because the upstream R2 bucket only honors GET-with-redirect, but
the wget call in the Dockerfile uses GET so the original URL was never
actually broken — it was just stale.

Switch to an ARG so future bumps are a single --build-arg override.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

containers/Dockerfile

@@ -168,6 +168,7 @@ ENV VIRTUAL_ENV="/app/.venv"
 
 WORKDIR /app
 
+ARG CAIDO_VERSION=0.56.0
 RUN ARCH=$(uname -m) && \
     if [ "$ARCH" = "x86_64" ]; then \
         CAIDO_ARCH="x86_64"; \
@@ -176,7 +177,7 @@ RUN ARCH=$(uname -m) && \
     else \
         echo "Unsupported architecture: $ARCH" && exit 1; \
     fi && \
-    wget -O caido-cli.tar.gz https://caido.download/releases/v0.48.0/caido-cli-v0.48.0-linux-${CAIDO_ARCH}.tar.gz && \
+    wget -O caido-cli.tar.gz "https://caido.download/releases/v${CAIDO_VERSION}/caido-cli-v${CAIDO_VERSION}-linux-${CAIDO_ARCH}.tar.gz" && \
     tar -xzf caido-cli.tar.gz && \
     chmod +x caido-cli && \
     rm caido-cli.tar.gz && \