Initial commit: CSSS 590 attendance tracker

Publish review_attendance.py, the email and failed-message templates,
and the example config used to track CSSS 590 seminar attendance and
send warning DMs through the Canvas Conversations API. README walks
through the weekly workflow, the Roll Call CSV quirks worth knowing
about, and what must stay out of git.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,19 @@
+# Real configuration (contains Canvas API token + course-specific IDs).
+config.toml
+
+# Student data — never commit any of this.
+attendance_reports_*.csv
+students_contacted.tsv
+attendance_summary.csv
+
+# Common archival material your working dir may collect.
+screenshot-*.png
+*.pdf
+*.svg
+
+# Python bytecode.
+__pycache__/
+*.pyc
+
+# md2html preview output.
+*.html