Math tracker (/trackers/math): Evan Chen's Napkin, chapter by chapter

Schema math (parts, chapters, sections, activity), seeded with all 100 chapters
(Ch 0-94, appendix A-E), 647 sections, PDF pages, exercise counts and approximate
prereqs. Triggers stamp started_at/completed_at and log status/exercise/note/section
changes; math.apply_progress(jsonb) applies the JSON format bots send. Private by
default via MATH_PRIVATE in #lib/math (owner-only prefix + lock in every tracker list).
Overall + per-part progress, current chapter, prereq hints, quick status buttons,
exercises stepper, notes, optional section ticks, activity log, dependency chart.
Deploy preflight checks the math schema (4 tables, 100 chapters).

src/lib/tracker-icons.ts

@@ -96,6 +96,13 @@ export const trackerIcons: Record<string, TrackerIcon> = {
 			'M20 3v4M22 5h-4M4 17v2M5 18H3'
 		]
 	},
+	math: {
+		from: '#818cf8',
+		to: '#4338ca',
+		ink: WHITE,
+		// sigma
+		paths: ['M18 7V4H6l6 8-6 8h12v-3']
+	},
 	notes: {
 		from: '#fde68a',
 		to: '#f59e0b',