fix: correct dose ID generation for empty takenBy arrays (#105)

The takenBy field is a string[]. Empty arrays [] are truthy in JavaScript,
causing d.takenBy ? [...] patterns to generate dose IDs with trailing
hyphens (e.g., '5-0-173...-') instead of base IDs ('5-0-173...').

This mismatch between ID generation and computeMissedPastDoseIds (which
correctly uses .length > 0) caused doses to always appear as missed.

Changes:
- Add expandDoseIds() helper function using correct .length > 0 check
- Replace 8 buggy inline patterns in DashboardPage.tsx
- Refactor SchedulePage.tsx to use shared expandDoseIds()
- Add backend startup repair to strip trailing hyphens from existing IDs
- Add 12 new tests (6 frontend + 6 backend)

frontend/src/test/utils/schedule.test.ts

@@ -4,6 +4,7 @@ import {
 	buildSchedulePreview,
 	calculateCoverage,
 	computeMissedPastDoseIds,
+	expandDoseIds,
 	getNextReminderForMed,
 	getReminderStatusText,
 	getStockStatus,
@@ -1147,3 +1148,52 @@ function groupEventsIntoPastDays(
 		meds: Array.from(medMap.entries()).map(([medName, doses]) => ({ medName, doses })),
 	}));
 }
+
+describe("expandDoseIds", () => {
+	it("returns base IDs when takenBy is empty array", () => {
+		const doses = [
+			{ id: "1-0-1729123200000", takenBy: [] as string[] },
+			{ id: "2-0-1729123200000", takenBy: [] as string[] },
+		];
+		const result = expandDoseIds(doses);
+		expect(result).toEqual(["1-0-1729123200000", "2-0-1729123200000"]);
+	});
+
+	it("returns person-suffixed IDs when takenBy has entries", () => {
+		const doses = [{ id: "1-0-1729123200000", takenBy: ["Alice"] }];
+		const result = expandDoseIds(doses);
+		expect(result).toEqual(["1-0-1729123200000-Alice"]);
+	});
+
+	it("returns multiple IDs for multiple takenBy entries", () => {
+		const doses = [{ id: "1-0-1729123200000", takenBy: ["Alice", "Bob"] }];
+		const result = expandDoseIds(doses);
+		expect(result).toEqual(["1-0-1729123200000-Alice", "1-0-1729123200000-Bob"]);
+	});
+
+	it("handles mix of empty and non-empty takenBy", () => {
+		const doses = [
+			{ id: "1-0-1729123200000", takenBy: ["Alice"] },
+			{ id: "2-0-1729123200000", takenBy: [] as string[] },
+			{ id: "3-0-1729123200000", takenBy: ["Bob", "Carol"] },
+		];
+		const result = expandDoseIds(doses);
+		expect(result).toEqual([
+			"1-0-1729123200000-Alice",
+			"2-0-1729123200000",
+			"3-0-1729123200000-Bob",
+			"3-0-1729123200000-Carol",
+		]);
+	});
+
+	it("returns empty array for empty doses", () => {
+		expect(expandDoseIds([])).toEqual([]);
+	});
+
+	it("handles non-array takenBy gracefully", () => {
+		// In case of unexpected data, treat non-array as empty
+		const doses = [{ id: "1-0-1729123200000", takenBy: null as unknown as string[] }];
+		const result = expandDoseIds(doses);
+		expect(result).toEqual(["1-0-1729123200000"]);
+	});
+});