feat(media): add public URL generation for media files and improve S3 integration

Introduce `getPublicUrl` in `S3Service` for generating public URLs. Replace custom file URL generation logic across services with the new method. Add media controller for file streaming and update related tests. Adjust frontend to display user roles instead of email in the sidebar. Update environment schema to include optional `API_URL`. Fix help page contact email.

backend/src/media/media.controller.spec.ts

@@ -0,0 +1,60 @@
+import { Readable } from "node:stream";
+import { NotFoundException } from "@nestjs/common";
+import { Test, TestingModule } from "@nestjs/testing";
+import { S3Service } from "../s3/s3.service";
+import { MediaController } from "./media.controller";
+
+describe("MediaController", () => {
+	let controller: MediaController;
+	let s3Service: S3Service;
+
+	const mockS3Service = {
+		getFileInfo: jest.fn(),
+		getFile: jest.fn(),
+	};
+
+	beforeEach(async () => {
+		const module: TestingModule = await Test.createTestingModule({
+			controllers: [MediaController],
+			providers: [{ provide: S3Service, useValue: mockS3Service }],
+		}).compile();
+
+		controller = module.get<MediaController>(MediaController);
+		s3Service = module.get<S3Service>(S3Service);
+	});
+
+	it("should be defined", () => {
+		expect(controller).toBeDefined();
+	});
+
+	describe("getFile", () => {
+		it("should stream the file and set headers", async () => {
+			const res = {
+				setHeader: jest.fn(),
+			} as any;
+			const stream = new Readable();
+			stream.pipe = jest.fn();
+
+			mockS3Service.getFileInfo.mockResolvedValue({
+				size: 100,
+				metaData: { "content-type": "image/webp" },
+			});
+			mockS3Service.getFile.mockResolvedValue(stream);
+
+			await controller.getFile("test.webp", res);
+
+			expect(res.setHeader).toHaveBeenCalledWith("Content-Type", "image/webp");
+			expect(res.setHeader).toHaveBeenCalledWith("Content-Length", 100);
+			expect(stream.pipe).toHaveBeenCalledWith(res);
+		});
+
+		it("should throw NotFoundException if file is not found", async () => {
+			mockS3Service.getFileInfo.mockRejectedValue(new Error("Not found"));
+			const res = {} as any;
+
+			await expect(controller.getFile("invalid", res)).rejects.toThrow(
+				NotFoundException,
+			);
+		});
+	});
+});