refactor(01-05): rewrite Application.kt with ContentNegotiation, Flyway boot, /health

- Remove wildcard Ktor imports (D-11 allWarningsAsErrors safety) — all imports explicit
- Install ContentNegotiation { json() } for @Serializable response bodies
- Call Database.migrate(this) at boot — fails loudly if Postgres unreachable
- Extract configureRouting() extension so tests can compose routing without DB
- Replace template root greeting with GET /health → {"status":"ok"} (D-16)
- main() shape unchanged: embeddedServer(Netty, SERVER_PORT, "0.0.0.0", ...)

server/src/main/kotlin/dev/ulfrx/recipe/Application.kt

@@ -1,20 +1,36 @@
 package dev.ulfrx.recipe
 
-import io.ktor.server.application.*
-import io.ktor.server.engine.*
-import io.ktor.server.netty.*
-import io.ktor.server.response.*
-import io.ktor.server.routing.*
+import io.ktor.serialization.kotlinx.json.json
+import io.ktor.server.application.Application
+import io.ktor.server.application.install
+import io.ktor.server.engine.embeddedServer
+import io.ktor.server.netty.Netty
+import io.ktor.server.plugins.contentnegotiation.ContentNegotiation
+import io.ktor.server.response.respond
+import io.ktor.server.routing.get
+import io.ktor.server.routing.routing
+import kotlinx.serialization.Serializable
 
 fun main() {
     embeddedServer(Netty, port = SERVER_PORT, host = "0.0.0.0", module = Application::module)
         .start(wait = true)
 }
 
+@Serializable
+private data class Health(val status: String)
+
 fun Application.module() {
+    install(ContentNegotiation) {
+        json()
+    }
+    Database.migrate(this)
+    configureRouting()
+}
+
+fun Application.configureRouting() {
     routing {
-        get("/") {
-            call.respondText("Ktor: ${Greeting().greet()}")
+        get("/health") {
+            call.respond(Health(status = "ok"))
         }
     }
-}
+}