feat: Introduce Result type and update UI states

This commit introduces a generic `Result` sealed interface to represent success, error, and loading states for asynchronous operations. It also updates the home screen UI and ViewModel to utilize this `Result` type for displaying different states.

Key changes:
- Added `Result.kt` in `core:util` defining the `Result` sealed interface and an `asResult()` Flow extension.
- Updated `HomeScreenViewModel` to use `asResult()` and map the `ObserveAirportsUseCase` output to `HomeUiState` (Loading, Success, Error).
- Modified `HomeUiState` to be a sealed interface with `Loading`, `Success`, and `Error` subtypes.
- Updated `HomeScreen` to handle different `HomeUiState` values and display appropriate UI (Loading text, Error text, or list of airports).
- Added `core.util` dependency to `ui:home`.
- Updated Moshi and Retrofit Moshi converter dependencies in `model/data/api/build.gradle.kts` and `gradle/libs.versions.toml`.
- Added `moshi` and `moshiKotlinCodegen` versions to `gradle/libs.versions.toml`.
- Removed `converter-moshi` and added `retrofit-converter-moshi` in `gradle/libs.versions.toml`.
- Added `ksp(libs.moshi.kotlin.codegen)` to `model/data/api/build.gradle.kts`.
- Added `INTERNET` permission to `app/src/main/AndroidManifest.xml`.
- Updated `ObserveAirportsUseCaseImpl` to use `cacheKey` when setting airports info and to fetch airports for "pl" (lowercase).
- Added `.editorconfig` file with Kotlin trailing comma settings.

core/util/src/main/kotlin/dev/adriankuta/flights/core/util/Result.kt

@@ -0,0 +1,16 @@
+package dev.adriankuta.flights.core.util
+
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.catch
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.onStart
+
+sealed interface Result<out T> {
+    data class Success<T>(val data: T) : Result<T>
+    data class Error(val exception: Throwable) : Result<Nothing>
+    data object Loading : Result<Nothing>
+}
+
+fun <T> Flow<T>.asResult(): Flow<Result<T>> = map<T, Result<T>> { Result.Success(it) }
+    .onStart { emit(Result.Loading) }
+    .catch { emit(Result.Error(it)) }