Add Docker, bash launcher, and Linux-first README

Lets the project be served as a web app from a Linux host in one command:
- Dockerfile (python:3.12-slim + non-root user + streamlit healthcheck)
- docker-compose.yml with env_file, restart policy, configurable HOST_PORT,
  and an optional CA-bundle volume for self-signed GPFS GUIs
- .dockerignore to keep the image lean
- run.sh for native (non-Docker) runs: creates a venv on first use and
  launches either the Streamlit UI (default) or the REPL
- .gitattributes pins LF line endings on shell/yaml/py so scripts stay
  executable when checked out on Linux from a Windows host
- README rewritten with Linux/Docker quick starts in front, Windows behind

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,9 @@
+* text=auto eol=lf
+*.sh    text eol=lf
+Dockerfile text eol=lf
+*.yml   text eol=lf
+*.yaml  text eol=lf
+*.py    text eol=lf
+*.md    text eol=lf
+*.txt   text eol=lf
+.env.example text eol=lf