refactor(core): Unify components and adopt standard tooling

This commit performs several key refactorings within the `core`-module to improve consistency, stability, and adhere to industry best practices.

1.  **Unify `Result` Type:**
    Removed the specialized `Result<T>` class from `core-utils`. The entire system will now exclusively use the more flexible and type-safe `Result<T, E>` from `core-domain`. This allows for explicit, non-exception-based error handling for business logic.

2.  **Adopt Flyway for Database Migrations:**
    Replaced the custom `DatabaseMigrator.kt` implementation with the industry-standard tool Flyway. The `DatabaseFactory` now triggers Flyway migrations on application startup. This provides more robust, transactional, and feature-rich schema management.

3.  **Cleanup and Housekeeping:**
    - Removed obsolete test files related to the old migrator.
    - Ensured all components align with the new unified patterns.

BREAKING CHANGE: The `at.mocode.core.utils.error.Result` class has been removed. All modules must be updated to use the `at.mocode.core.domain.error.Result` type. The custom migrator is no longer available.

Closes #ISSUE_NUMBER_FOR_REFACTORING

masterdata/masterdata-api/src/main/kotlin/at/mocode/masterdata/api/StatusPages.kt

@@ -0,0 +1,48 @@
+package at.mocode.masterdata.api
+
+import at.mocode.core.domain.model.ApiResponse
+import io.ktor.http.*
+import io.ktor.server.application.*
+import io.ktor.server.plugins.statuspages.*
+import io.ktor.server.response.*
+
+// Eine einfache, eigene Exception, um "Nicht gefunden"-Fälle klarer zu machen.
+class NotFoundException(message: String) : RuntimeException(message)
+
+fun Application.configureStatusPages() {
+    install(StatusPages) {
+
+        // Regel 1: Fange alle "IllegalArgumentException" ab.
+        // Das passiert bei ungültigen Eingaben, z.B. ein falsches UUID-Format.
+        exception<IllegalArgumentException> { call, cause ->
+            log.warn("Bad Request: ${cause.message}")
+            val errorResponse = ApiResponse<Unit>(
+                message = cause.message ?: "Invalid input provided.",
+                errors = listOf("BAD_REQUEST")
+            )
+            call.respond(HttpStatusCode.BadRequest, errorResponse)
+        }
+
+        // Regel 2: Fange unsere eigene "NotFoundException" ab.
+        // Diese werfen wir, wenn eine Entität nicht in der DB gefunden wurde.
+        exception<NotFoundException> { call, cause ->
+            log.info("Resource not found: ${cause.message}")
+            val errorResponse = ApiResponse<Unit>(
+                message = cause.message ?: "The requested resource was not found.",
+                errors = listOf("NOT_FOUND")
+            )
+            call.respond(HttpStatusCode.NotFound, errorResponse)
+        }
+
+        // Regel 3: Fange alle anderen, unerwarteten Fehler ab.
+        // Das ist unser Sicherheitsnetz für alles, was wir nicht vorhergesehen haben.
+        exception<Throwable> { call, cause ->
+            log.error("Internal Server Error", cause) // Logge den kompletten Stacktrace
+            val errorResponse = ApiResponse<Unit>(
+                message = "An unexpected internal server error occurred.",
+                errors = listOf("INTERNAL_SERVER_ERROR")
+            )
+            call.respond(HttpStatusCode.InternalServerError, errorResponse)
+        }
+    }
+}

masterdata/masterdata-api/src/main/kotlin/at/mocode/masterdata/api/rest/AltersklasseController.kt

@@ -91,7 +91,7 @@ class AltersklasseController(
                         } catch (_: Exception) {
                             return@get call.respond(
                                 HttpStatusCode.BadRequest,
-                                ApiResponse.error<List<AltersklasseDto>>("Invalid sparte parameter: $it")
+                                ApiResponse<List<AltersklasseDto>>("Invalid sparte parameter: $it")
                             )
                         }
                     }
@@ -103,7 +103,7 @@ class AltersklasseController(
                         } else {
                             return@get call.respond(
                                 HttpStatusCode.BadRequest,
-                                ApiResponse.error<List<AltersklasseDto>>("Invalid geschlecht parameter. Must be 'M' or 'W'")
+                                ApiResponse<List<AltersklasseDto>>("Invalid geschlecht parameter. Must be 'M' or 'W'")
                             )
                         }
                     }