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>

run.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+cd "$(dirname "$0")"
+
+if [[ ! -f .env ]]; then
+    echo "No .env found. Copy .env.example to .env and edit it first." >&2
+    exit 1
+fi
+
+if [[ ! -d .venv ]]; then
+    echo "Creating virtualenv at .venv..."
+    python3 -m venv .venv
+    .venv/bin/pip install -q --upgrade pip
+    .venv/bin/pip install -q -r requirements.txt
+fi
+
+MODE="${1:-web}"
+HOST="${HOST:-0.0.0.0}"
+PORT="${PORT:-8501}"
+
+case "$MODE" in
+    web)
+        exec .venv/bin/streamlit run gpfs_agent/web.py \
+            --server.address "$HOST" \
+            --server.port "$PORT" \
+            --server.headless true \
+            --browser.gatherUsageStats false
+        ;;
+    cli|repl)
+        exec .venv/bin/python -m gpfs_agent
+        ;;
+    *)
+        echo "Usage: $0 [web|cli]" >&2
+        exit 2
+        ;;
+esac