Refactor: Update package structure and implement bottom navigation

This commit refactors the package structure for Gradle convention plugins and introduces bottom navigation to the application.

Key changes:
- Moved Gradle convention plugin files from `dev.adriankuta.partymania` to `dev.adriankuta.flights`.
- Added `TopLevelDestination.kt` to define top-level navigation destinations with icons, titles, and routes.
- Implemented `FlightsBottomBar` Composable in `FlightsApp.kt` to display a `NavigationBar` with items for each `TopLevelDestination`.
- Updated `FlightsNavGraph.kt`:
    - Renamed from `FlightsNavGraph.kt` to `navigation/FlightsNavGraph.kt`.
    - Added `navigateToTopLevelDestination` extension function for `NavController` to handle navigation to top-level destinations with appropriate `NavOptions`.
- Updated `HomeNavigation.kt`:
    - Added `navigateToHome` extension function for `NavController`.
- Added `strings.xml` for `ui:home` module with `home_screen_title`.
- Ensured Kotlin serialization plugin is correctly applied in `app/build.gradle.kts`.

app/src/main/kotlin/dev/adriankuta/flights/ui/FlightsApp.kt

@@ -1,25 +1,75 @@
 package dev.adriankuta.flights.ui
 
 import androidx.compose.foundation.layout.padding
+import androidx.compose.material3.Icon
+import androidx.compose.material3.NavigationBar
+import androidx.compose.material3.NavigationBarDefaults
+import androidx.compose.material3.NavigationBarItem
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Surface
+import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.saveable.rememberSaveable
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
-import dev.adriankuta.flights.FlightsNavGraph
+import androidx.compose.ui.res.stringResource
+import androidx.navigation.NavHostController
+import androidx.navigation.compose.rememberNavController
+import dev.adriankuta.flights.navigation.FlightsNavGraph
+import dev.adriankuta.flights.navigation.TopLevelDestination
+import dev.adriankuta.flights.navigation.navigateToTopLevelDestination
 import dev.adriankuta.flights.ui.designsystem.theme.Elevation
 
 @Composable
 fun FlightsApp(
     modifier: Modifier = Modifier,
 ) {
+    val navController = rememberNavController()
+
     Surface(
         tonalElevation = Elevation.Surface,
         modifier = modifier,
     ) {
         Scaffold(
             snackbarHost = { InAppUpdates() },
+            bottomBar = {
+                FlightsBottomBar(
+                    navController = navController,
+                )
+            },
         ) { paddingValues ->
-            FlightsNavGraph(Modifier.padding(paddingValues))
+            FlightsNavGraph(
+                navController = navController,
+                modifier = Modifier.padding(paddingValues),
+            )
+        }
+    }
+}
+
+@Composable
+internal fun FlightsBottomBar(
+    navController: NavHostController = rememberNavController(),
+) {
+    var selectedDestination by rememberSaveable { mutableIntStateOf(0) }
+
+    NavigationBar(windowInsets = NavigationBarDefaults.windowInsets) {
+        TopLevelDestination.entries.forEachIndexed { index, destination ->
+            NavigationBarItem(
+                selected = selectedDestination == index,
+                onClick = {
+                    selectedDestination = index
+                    navController.navigateToTopLevelDestination(TopLevelDestination.HOME)
+                },
+                icon = {
+                    Icon(
+                        destination.icon,
+                        contentDescription = null,
+                    )
+                },
+                label = { Text(stringResource(destination.titleTextId)) },
+            )
         }
     }
 }