feat: add AQI/RAD help dialog on map screen

app/src/main/kotlin/org/db3/airmq/features/map/MapScreen.kt

@@ -119,19 +119,17 @@ private fun MapScreenContent(
         MapTopControls(
             selectedSensor = uiState.selectedTopSensor,
             onSensorSelected = { onEvent(Event.TopSensorSelected(it)) },
-            onHelpClick = {
-                Toast.makeText(
-                    context,
-                    context.getString(R.string.text_what_does_it_mean_title),
-                    Toast.LENGTH_SHORT
-                ).show()
-            },
+            onHelpClick = { onEvent(Event.HelpClicked) },
             modifier = Modifier
                 .align(Alignment.TopEnd)
                 .statusBarsPadding()
                 .padding(top = 20.dp, end = 16.dp)
         )
 
+        if (uiState.showHelpDialog) {
+            WhatDoesThisMeanDialog(onDismiss = { onEvent(Event.HelpDialogDismissed) })
+        }
+
         if (uiState.searchPanelState == null && uiState.devicePanelState == null) {
             MapFloatingActions(
                 onSearchClick = { onEvent(Event.SearchButtonClicked) },

app/src/main/kotlin/org/db3/airmq/features/map/MapScreenContract.kt

@@ -51,7 +51,8 @@ object MapScreenContract {
         val selectedTopSensor: SensorType = SensorType.DUST,
         val searchPanelState: SearchPanelState? = null,
         val devicePanelState: DevicePanelState? = null,
-        val selectedMarkerId: String? = null
+        val selectedMarkerId: String? = null,
+        val showHelpDialog: Boolean = false
     )
 
     sealed interface Action {
@@ -67,6 +68,8 @@ object MapScreenContract {
         data class SearchResultClicked(val resultId: String) : Event
         data object MyLocationClicked : Event
         data class TopSensorSelected(val sensor: SensorType) : Event
+        data object HelpClicked : Event
+        data object HelpDialogDismissed : Event
         data class MarkerClicked(val itemId: String) : Event
         data object DevicePanelClosed : Event
         data object DeviceOpenClicked : Event

app/src/main/kotlin/org/db3/airmq/features/map/MapUiComponents.kt

@@ -1,5 +1,6 @@
 package org.db3.airmq.features.map
 
+import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
 import androidx.compose.foundation.clickable
@@ -12,10 +13,13 @@ import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.wrapContentHeight
+import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.shape.CircleShape
+import androidx.compose.foundation.verticalScroll
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
@@ -27,6 +31,7 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.OutlinedTextField
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
+import androidx.compose.material3.TextButton
 import androidx.compose.animation.AnimatedVisibility
 import androidx.compose.animation.core.tween
 import androidx.compose.animation.expandVertically
@@ -38,6 +43,10 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.layout.ContentScale
+import androidx.compose.ui.unit.sp
+import androidx.compose.ui.window.Dialog
+import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.draw.rotate
 import androidx.compose.ui.graphics.Brush
@@ -220,6 +229,78 @@ fun MapTopControls(
     }
 }
 
+@Composable
+fun WhatDoesThisMeanDialog(
+    onDismiss: () -> Unit
+) {
+    Dialog(onDismissRequest = onDismiss) {
+        Card(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(horizontal = 32.dp, vertical = 128.dp),
+            shape = RoundedCornerShape(24.dp),
+            colors = CardDefaults.cardColors(containerColor = MaterialTheme.colorScheme.surface)
+        ) {
+            Column(
+                modifier = Modifier.padding(24.dp)
+            ) {
+                Text(
+                    text = stringResource(id = R.string.text_what_does_it_mean_title),
+                    style = MaterialTheme.typography.titleMedium,
+                    fontSize = 16.sp,
+                    fontWeight = FontWeight.Medium,
+                    modifier = Modifier.padding(bottom = 22.dp)
+                )
+                Column(
+                    modifier = Modifier
+                        .heightIn(max = 400.dp)
+                        .verticalScroll(rememberScrollState())
+                        .padding(horizontal = 0.dp)
+                ) {
+                    Text(
+                        text = stringResource(id = R.string.text_aqi_title),
+                        style = MaterialTheme.typography.bodyLarge,
+                        fontSize = 16.sp,
+                        fontWeight = FontWeight.Medium
+                    )
+                    Spacer(modifier = Modifier.height(16.dp))
+                    Text(
+                        text = stringResource(id = R.string.text_aqi),
+                        style = MaterialTheme.typography.bodyMedium
+                    )
+                    Spacer(modifier = Modifier.height(8.dp))
+                    Image(
+                        painter = painterResource(id = R.drawable.aqi_table),
+                        contentDescription = null,
+                        contentScale = ContentScale.Fit,
+                        modifier = Modifier
+                            .width(300.dp)
+                            .height(150.dp)
+                    )
+                    Spacer(modifier = Modifier.height(20.dp))
+                    Text(
+                        text = stringResource(id = R.string.text_rad_title),
+                        style = MaterialTheme.typography.bodyLarge,
+                        fontSize = 16.sp,
+                        fontWeight = FontWeight.Medium
+                    )
+                    Spacer(modifier = Modifier.height(16.dp))
+                    Text(
+                        text = stringResource(id = R.string.text_rad),
+                        style = MaterialTheme.typography.bodyMedium
+                    )
+                }
+                TextButton(
+                    onClick = onDismiss,
+                    modifier = Modifier.align(Alignment.End)
+                ) {
+                    Text(stringResource(id = R.string.button_ok))
+                }
+            }
+        }
+    }
+}
+
 @Composable
 private fun SensorTypeItem(
     iconRes: Int,

app/src/main/kotlin/org/db3/airmq/features/map/MapViewModel.kt

@@ -96,6 +96,14 @@ class MapViewModel @Inject constructor(
                 remapMarkers()
             }
 
+            Event.HelpClicked -> {
+                _uiState.value = _uiState.value.copy(showHelpDialog = true)
+            }
+
+            Event.HelpDialogDismissed -> {
+                _uiState.value = _uiState.value.copy(showHelpDialog = false)
+            }
+
             is Event.MarkerClicked -> {
                 val selectedItem = _uiState.value.items.firstOrNull { it.id == event.itemId } ?: return
                 _uiState.value = _uiState.value.copy(