fix: CRLF/BOM line endings + restart policies + gitattributes

- poller/docker-entrypoint.sh: convert from CRLF+BOM to LF (UTF-8 no BOM)
  Windows saved the file with a UTF-8 BOM which made the Linux kernel
  reject the shebang with 'exec format error', crashing the poller.

- infrastructure/openbao/init.sh: same CRLF -> LF fix

- poller/Dockerfile: add sed to strip CRLF and BOM at image build time
  as a defensive measure for future Windows edits

- docker-compose.override.yml: add 'restart: on-failure' to api and poller
  so they recover from the postgres startup race (TimescaleDB restarts
  postgres after initdb, briefly causing connection refused on first boot)

- .gitattributes: enforce LF for all text/script/code files so git
  normalises line endings on checkout and prevents this class of bug

infrastructure/openbao/init.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/sh
 # OpenBao Transit initialization script
 # Runs after OpenBao starts in dev mode