feat: Add deployment guide and update README for Coolify setup; include dotenv for environment variable management

tests/integration/mileage-engine-flow.test.ts

@@ -1,3 +1,5 @@
+import { GuildMember } from "discord.js";
+
 const mockClient = {
   query: jest.fn(),
   release: jest.fn(),
@@ -53,7 +55,7 @@ describe("MileageEngine flow", () => {
           }),
         },
       },
-    } as any;
+    } as unknown as GuildMember;
 
     const engine = new MileageEngine({
       databaseUrl: "postgres://test",