Further improve Dockerfile - Reduce Docker image size and simplify Dockerfile (attempt to)

[tCR-lux]

• for example switch to debian:trixie-slim,
• merge layers,
• avoid nvm in the runtime image,
• use --no-install-recommends for apt to avoid pulling in extra packages,
• add .dockerignore to keep build context small,
• ...
• multi-stage for Node/Mermaid.

[tCR-lux]

• first commit (bookworm:slim):

IMAGE ID DISK USAGE CONTENT SIZE EXTRA
flowintel:latest 863c19fd42cd 5.87GB 1.54GB

• same refactor but with ubuntu:noble again

IMAGE ID DISK USAGE CONTENT SIZE EXTRA
flowintel:latest 135c73309f26 6.37GB 1.71GB

• v4.0.0:

IMAGE ID DISK USAGE CONTENT SIZE EXTRA
flowintel:latest 96531be5700b 10.7GB 3.05GB

• ??? alpine ???
  • with current stack (LaTeX, pandoc, etc.), unlikely to be worth the attempt given the complexity !

The impact of multi-stage is seen on "disk usage", the impact of cleanup on "content size" (especially apt cleanup cache for the later).