Refactor: Introduce SearchForm and PassengersOptions composables

This commit refactors the HomeScreen by extracting the search form logic into a new `SearchForm` composable and the passenger selection into a `PassengersOptions` composable.

Key changes:
- Created `PassengersOptions.kt` with a composable function to handle adult, teen, and child passenger counts.
- Created `SearchForm.kt` with a composable function that encapsulates airport selection, date picking, passenger options, and the search button.
- Updated `HomeScreen.kt`:
    - Replaced the previous inline form layout with the new `SearchForm` composable.
    - Made the screen content vertically scrollable using `Box` and `verticalScroll`.
    - Passed a new `onSearch` lambda to the `HomeScreenContent`.
- Updated `HomeScreenViewModel.kt`:
    - Modified `updateAdultCount`, `updateTeenCount`, and `updateChildCount` to accept the new count directly instead of a diff.
    - Added a `search()` function (currently logs to Timber).
    - Ensured child count does not exceed adult count when adult count changes.
- Updated `Counter.kt` in `ui/sharedui`:
    - Changed `onCountChange` parameter to `onValueChange` which now receives the new absolute value.
    - Added a `maxVal` parameter to limit the maximum value of the counter.

ui/sharedui/src/main/kotlin/dev/adriankuta/flights/ui/sharedui/Counter.kt

@@ -34,10 +34,11 @@ import dev.adriankuta.flights.ui.designsystem.theme.FlightsTheme
 @Composable
 fun Counter(
     value: Int,
-    onCountChange: (diff: Int) -> Unit,
+    onValueChange: (newValue: Int) -> Unit,
     modifier: Modifier = Modifier,
     label: String? = null,
     minVal: Int = 0,
+    maxVal: Int = Int.MAX_VALUE,
 ) {
     val view = LocalView.current
 
@@ -84,7 +85,7 @@ fun Counter(
                 modifier = Modifier.weight(1f),
                 onClick = {
                     view.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP)
-                    onCountChange(-1)
+                    onValueChange(value - 1)
                 },
                 shape = MaterialTheme.shapes.medium,
                 enabled = value > minVal,
@@ -99,10 +100,10 @@ fun Counter(
                 modifier = Modifier.weight(1f),
                 onClick = {
                     view.performHapticFeedback(HapticFeedbackConstants.KEYBOARD_TAP)
-                    onCountChange(1)
+                    onValueChange(value + 1)
                 },
                 shape = MaterialTheme.shapes.medium,
-                enabled = value < 20,
+                enabled = value < maxVal,
             ) {
                 Text(
                     text = "+",
@@ -124,7 +125,8 @@ private fun CounterPreview() {
         Counter(
             value = tapCounter,
             label = "Taps",
-            onCountChange = { tapCounter += it },
+            onValueChange = { tapCounter += it },
+            maxVal = 20,
         )
     }
 }