test(01-05): rewrite ApplicationTest to assert GET /health without Postgres

- Replace testRoot template assertion with 'health endpoint returns 200 with status ok'
- Compose only configureRouting() in testApplication — NOT Application.module()
- This keeps the test independent of Database.migrate / running Postgres (D-11 test invariant)
- Install ContentNegotiation { json() } inside application { } — production module() does it,
  but the test composes routing directly and must install the plugin itself
- All imports explicit (D-11 allWarningsAsErrors); no wildcards
- Body checked via substring for "status" + "ok" — robust to JSON field ordering

Note: ./gradlew :server:test runtime verification deferred to Plan 07 (integration build)
since build-logic/recipe.jvm.server plugin is being authored in parallel Plan 02 worktree.

server/src/test/kotlin/dev/ulfrx/recipe/ApplicationTest.kt

@@ -1,20 +1,30 @@
 package dev.ulfrx.recipe
 
-import io.ktor.client.request.*
-import io.ktor.client.statement.*
-import io.ktor.http.*
-import io.ktor.server.testing.*
-import kotlin.test.*
+import io.ktor.client.request.get
+import io.ktor.client.statement.bodyAsText
+import io.ktor.http.HttpStatusCode
+import io.ktor.serialization.kotlinx.json.json
+import io.ktor.server.application.install
+import io.ktor.server.plugins.contentnegotiation.ContentNegotiation
+import io.ktor.server.testing.testApplication
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
 
 class ApplicationTest {
 
     @Test
-    fun testRoot() = testApplication {
+    fun `health endpoint returns 200 with status ok`() = testApplication {
         application {
-            module()
+            install(ContentNegotiation) {
+                json()
+            }
+            configureRouting()
         }
-        val response = client.get("/")
+        val response = client.get("/health")
         assertEquals(HttpStatusCode.OK, response.status)
-        assertEquals("Ktor: ${Greeting().greet()}", response.bodyAsText())
+        val body = response.bodyAsText()
+        assertTrue(body.contains("\"status\""), "expected body to contain status field, was: $body")
+        assertTrue(body.contains("\"ok\""), "expected body to contain ok value, was: $body")
     }
 }