fix: treat PID=1 as stale in PID file singleton check, fix govet shadow, add .gitattributes (#2642)

- pid: When a container stops and leaves behind a PID file with PID 1
  on a shared volume, the host's init process (PID 1) passes the
  isProcessRunning check, blocking new gateway starts. Treat recorded
  PID 1 as always stale in both WritePidFile and ReadPidFileWithCheck.
  Added unit tests covering the PID=1 container leftover scenario.

- isolation: Fix govet shadow warning on platform_windows.go line 105
  where := shadows the outer err variable. Changed to = assignment.

- gitattributes: Enforce LF line endings for shell scripts to prevent
  CRLF issues when checking out on Windows (breaks Docker entrypoint).

Co-authored-by: BeaconCat <BeaconCat@users.noreply.github.com>

.gitattributes

@@ -0,0 +1,3 @@
+# Ensure shell scripts always use LF line endings regardless of OS.
+*.sh text eol=lf
+docker/entrypoint.sh text eol=lf