refactor: deduplicate formatters and improve test mocks (#81)

- Consolidate duplicate date formatting utilities
- Use shared formatters across backend and frontend
- Clean up test mocks to use consistent test data
- Remove redundant formatting functions

frontend/src/test/utils/formatters.test.ts

@@ -5,9 +5,7 @@ import {
 	compareSemver,
 	deriveTotal,
 	formatDateTime,
-	formatFullBlisters,
 	formatNumber,
-	formatOpenBlisterAndLoose,
 	getBlisterStock,
 	getExpiryClass,
 	pad2,
@@ -227,22 +225,6 @@ describe("getBlisterStock", () => {
 	});
 });
 
-describe("formatFullBlisters", () => {
-	it("formats count without pill info", () => {
-		expect(formatFullBlisters({ fullBlisters: 5, openBlisterPills: 3, loosePills: 3 })).toBe("5");
-	});
-
-	it("formats count with pill info", () => {
-		expect(formatFullBlisters({ fullBlisters: 5, openBlisterPills: 3, loosePills: 3 }, 10)).toBe("5 (50)");
-	});
-});
-
-describe("formatOpenBlisterAndLoose", () => {
-	it("formats open blister pills count", () => {
-		expect(formatOpenBlisterAndLoose({ fullBlisters: 5, openBlisterPills: 7, loosePills: 7 })).toBe("7");
-	});
-});
-
 describe("compareSemver", () => {
 	it("returns 0 for equal versions", () => {
 		expect(compareSemver("1.2.3", "1.2.3")).toBe(0);