feat: migrate to Next.js for Mini App and enhance project structure

- Replaced the previous webapp with a new Mini App built using Next.js, improving performance and maintainability.
- Updated the `.gitignore` to exclude Next.js build artifacts and node modules.
- Revised documentation in `AGENTS.md`, `README.md`, and `architecture.md` to reflect the new Mini App structure and technology stack.
- Enhanced Dockerfile to support the new build process for the Next.js application.
- Updated CI workflow to build and test the Next.js application.
- Added new configuration options for the Mini App, including `MINI_APP_SHORT_NAME` for improved deep linking.
- Refactored frontend testing setup to accommodate the new structure and testing framework.
- Removed legacy webapp files and dependencies to streamline the project.

webapp-next/src/components/calendar/DayIndicators.test.tsx

@@ -0,0 +1,70 @@
+/**
+ * Unit tests for DayIndicators: rounding is position-based (first / last / only child),
+ * not by indicator type, so multiple segments form one pill.
+ */
+
+import { describe, it, expect } from "vitest";
+import { render } from "@testing-library/react";
+import { DayIndicators } from "./DayIndicators";
+
+const baseProps = {
+  dutyCount: 0,
+  unavailableCount: 0,
+  vacationCount: 0,
+  hasEvents: false,
+};
+
+describe("DayIndicators", () => {
+  it("renders nothing when no indicators", () => {
+    const { container } = render(<DayIndicators {...baseProps} />);
+    expect(container.firstChild).toBeNull();
+  });
+
+  it("renders one segment with only-child rounding (e.g. vacation only)", () => {
+    const { container } = render(
+      <DayIndicators {...baseProps} vacationCount={1} />
+    );
+    const wrapper = container.querySelector("[aria-hidden]");
+    expect(wrapper).toBeInTheDocument();
+    expect(wrapper?.className).toContain("[&>:only-child]:rounded-full");
+    const spans = wrapper?.querySelectorAll("span");
+    expect(spans).toHaveLength(1);
+  });
+
+  it("renders two segments with positional rounding (duty + vacation)", () => {
+    const { container } = render(
+      <DayIndicators {...baseProps} dutyCount={1} vacationCount={1} />
+    );
+    const wrapper = container.querySelector("[aria-hidden]");
+    expect(wrapper).toBeInTheDocument();
+    expect(wrapper?.className).toContain(
+      "[&>:first-child:not(:only-child)]:rounded-l-[3px]"
+    );
+    expect(wrapper?.className).toContain(
+      "[&>:last-child:not(:only-child)]:rounded-r-[3px]"
+    );
+    const spans = wrapper?.querySelectorAll("span");
+    expect(spans).toHaveLength(2);
+  });
+
+  it("renders three segments with first left-rounded, last right-rounded (duty + unavailable + vacation)", () => {
+    const { container } = render(
+      <DayIndicators
+        {...baseProps}
+        dutyCount={1}
+        unavailableCount={1}
+        vacationCount={1}
+      />
+    );
+    const wrapper = container.querySelector("[aria-hidden]");
+    expect(wrapper).toBeInTheDocument();
+    expect(wrapper?.className).toContain(
+      "[&>:first-child:not(:only-child)]:rounded-l-[3px]"
+    );
+    expect(wrapper?.className).toContain(
+      "[&>:last-child:not(:only-child)]:rounded-r-[3px]"
+    );
+    const spans = wrapper?.querySelectorAll("span");
+    expect(spans).toHaveLength(3);
+  });
+});