.gitattributes: LF-by-default + CRLF for .bat/.ps1, mark binaries

Without this, Windows clients commit CRLF and Linux CI runner can't
parse YAML/IS/shell scripts cleanly. Binaries (dll/sys/exe/zip/ico)
are explicitly marked so git doesn't try to text-normalize them
(critical for embedded WinDivert.sys in third_party/).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitattributes

@@ -0,0 +1,29 @@
+# Ensure LF line endings in repository for cross-platform CI builds.
+# Without this, Windows clients commit CRLF and the Linux runner can't
+# parse YAML / Inno Setup scripts / shell heredocs reliably.
+
+* text=auto eol=lf
+
+# Explicit LF for source code and configs.
+*.go    text eol=lf
+*.yml   text eol=lf
+*.yaml  text eol=lf
+*.toml  text eol=lf
+*.json  text eol=lf
+*.md    text eol=lf
+*.sh    text eol=lf
+*.iss   text eol=lf
+*.bat   text eol=crlf
+*.ps1   text eol=crlf
+
+# Binaries — never normalize.
+*.dll       binary
+*.sys       binary
+*.lib       binary
+*.exe       binary
+*.png       binary
+*.jpg       binary
+*.ico       binary
+*.bin       binary
+*.zip       binary
+*.7z        binary