refactor(ui): extract shared ExposedDropdownField (issue #796) (#815)

DropdownField (ConfigScreen) and PluginProviderDropdown (PluginsScreen)
were byte-for-byte identical. Extract into ui/common/ExposedDropdownField
and route both call sites to it. No behavior change.

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/ui/plugins/PluginsScreen.kt

@@ -13,7 +13,6 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.lazy.LazyColumn
 import androidx.compose.foundation.lazy.items
-import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Delete
 import androidx.compose.material.icons.filled.InstallDesktop
@@ -24,11 +23,7 @@ import androidx.compose.material3.Button
 import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Card
 import androidx.compose.material3.CircularProgressIndicator
-import androidx.compose.material3.DropdownMenuItem
 import androidx.compose.material3.ExperimentalMaterial3Api
-import androidx.compose.material3.ExposedDropdownMenuAnchorType
-import androidx.compose.material3.ExposedDropdownMenuBox
-import androidx.compose.material3.ExposedDropdownMenuDefaults
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
@@ -56,6 +51,7 @@ import com.m57.hermescontrol.theme.LocalHermesStatusColors
 import com.m57.hermescontrol.ui.common.DetailDialog
 import com.m57.hermescontrol.ui.common.EmptyState
 import com.m57.hermescontrol.ui.common.ErrorState
+import com.m57.hermescontrol.ui.common.ExposedDropdownField
 import com.m57.hermescontrol.ui.common.HermesScaffold
 import com.m57.hermescontrol.ui.common.NavIcon
 import com.m57.hermescontrol.ui.common.SearchBar
@@ -247,7 +243,7 @@ private fun ProviderSelectionSection(
                 style = MaterialTheme.typography.labelMedium,
             )
             Spacer(modifier = Modifier.height(4.dp))
-            PluginProviderDropdown(
+            ExposedDropdownField(
                 label = stringResource(R.string.plugins_memory_provider_label),
                 options =
                     listOf(
@@ -276,7 +272,7 @@ private fun ProviderSelectionSection(
                 style = MaterialTheme.typography.labelMedium,
             )
             Spacer(modifier = Modifier.height(4.dp))
-            PluginProviderDropdown(
+            ExposedDropdownField(
                 label = stringResource(R.string.plugins_context_engine_label),
                 options = listOf("compressor") + state.contextOptions.map { it.name },
                 selectedValue = state.contextEngine,
@@ -302,51 +298,6 @@ private fun ProviderSelectionSection(
     }
 }
 
-@OptIn(ExperimentalMaterial3Api::class)
-@Composable
-private fun PluginProviderDropdown(
-    label: String,
-    options: List<String>,
-    selectedValue: String,
-    onOptionSelected: (String) -> Unit,
-) {
-    var expanded by remember { mutableStateOf(false) }
-
-    ExposedDropdownMenuBox(
-        expanded = expanded,
-        onExpandedChange = { expanded = it },
-    ) {
-        OutlinedTextField(
-            value = selectedValue.ifEmpty { options.firstOrNull() ?: "" },
-            onValueChange = {},
-            readOnly = true,
-            modifier =
-                Modifier
-                    .fillMaxWidth()
-                    .menuAnchor(ExposedDropdownMenuAnchorType.PrimaryNotEditable),
-            label = { Text(label) },
-            trailingIcon = { ExposedDropdownMenuDefaults.TrailingIcon(expanded = expanded) },
-            singleLine = true,
-            shape = RoundedCornerShape(8.dp),
-        )
-
-        ExposedDropdownMenu(
-            expanded = expanded,
-            onDismissRequest = { expanded = false },
-        ) {
-            options.forEach { option ->
-                DropdownMenuItem(
-                    text = { Text(option) },
-                    onClick = {
-                        onOptionSelected(option)
-                        expanded = false
-                    },
-                )
-            }
-        }
-    }
-}
-
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
 private fun InstallSection(