Show the version in a footer for logged-in users

The version is read once at startup from the VERSION file, which is now
also copied into the Docker image. The footer is right-aligned below the
content block and only shown to logged-in users, so anonymous visitors
do not learn the exact version.

The startup log now has "Max starting." at the beginning of main() and
"Max initialized, version X." at the end, so a failed startup is visible
by the missing second line.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile

@@ -32,6 +32,7 @@ ENV MAX_PRODUCTION=1
 # Owned by root, so the app cannot modify its own code
 COPY max/ ./max
 COPY scripts/prod/ .
+COPY VERSION .
 # Precompile, since the app cannot write __pycache__ at runtime
 RUN python -m compileall -q max