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

.gitattributes

@@ -0,0 +1,23 @@
+# Enforce Unix line endings for shell scripts and other Linux-executed files
+*.sh text eol=lf
+*.py text eol=lf
+Dockerfile* text eol=lf
+*.conf text eol=lf
+*.sql text eol=lf
+*.go text eol=lf
+*.ts text eol=lf
+*.tsx text eol=lf
+*.json text eol=lf
+*.yaml text eol=lf
+*.yml text eol=lf
+*.md text eol=lf
+*.toml text eol=lf
+*.env* text eol=lf
+
+# Binary files - no line ending conversion
+*.png binary
+*.jpg binary
+*.ico binary
+*.woff binary
+*.woff2 binary
+*.ttf binary