chore: add .gitattributes + unit tests for ffprobe rational parser

LF normalization across OSes; *.sql pinned to LF for stable diffs.

Tests cover the rational frame-rate parser (NTSC 29.97, integer fps,
slow-mo 240, ffprobe's 0/0 unknown sentinel, malformed and out-of-range
inputs). Extracted the closure into a free fn for the test seam.

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

.gitattributes

@@ -0,0 +1,9 @@
+# Normalize line endings in the repo to LF. Windows checkouts can still
+# present working-copy files as CRLF; this just keeps the committed history
+# stable so contributors on any OS don't see whitespace-only diffs every
+# time someone touches a file.
+* text=auto eol=lf
+
+# Migrations and SQL must be LF — SQLite parsers don't care, but diffing
+# is much cleaner with stable endings.
+*.sql text eol=lf