feat: configurable bottom navigation bar (Issue #23)

## What
Adds a new Navigation Bar section to Settings where users can customize which items appear in the bottom navigation bar.

## Features
- Pick from any of the 19 drawer screens (max 5 items)
- Remove items with a close/delete button
- Items persist via SharedPreferences (CSV format)
- Invalid names are silently dropped
- Existing screens and auth-aware filtering respected

Closes #23

app/src/main/java/com/m57/hermescontrol/ui/settings/SettingsScreen.kt

@@ -5,6 +5,7 @@ import androidx.compose.animation.AnimatedVisibility
 import androidx.compose.animation.fadeIn
 import androidx.compose.animation.fadeOut
 import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
@@ -17,6 +18,8 @@ import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.text.KeyboardOptions
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.filled.Add
+import androidx.compose.material.icons.filled.Close
 import androidx.compose.material.icons.filled.Visibility
 import androidx.compose.material.icons.filled.VisibilityOff
 import androidx.compose.material3.Button
@@ -24,6 +27,8 @@ import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Card
 import androidx.compose.material3.CardDefaults
 import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.DropdownMenu
+import androidx.compose.material3.DropdownMenuItem
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
@@ -227,6 +232,60 @@ fun SettingsScreen(
                 }
             }
 
+            // Navigation Bar section
+            SectionCard(title = "Navigation Bar") {
+                Text(
+                    text = "Bottom bar items (${state.selectedNavItems.size}/5)",
+                    style = MaterialTheme.typography.bodyMedium,
+                )
+                Spacer(modifier = Modifier.height(8.dp))
+
+                state.selectedNavItems.forEach { name ->
+                    val label = viewModel.availableNavItems.firstOrNull { it.first == name }?.second ?: name
+                    Row(
+                        modifier = Modifier.fillMaxWidth().padding(vertical = 2.dp),
+                        horizontalArrangement = Arrangement.SpaceBetween,
+                        verticalAlignment = Alignment.CenterVertically,
+                    ) {
+                        Text(text = label, style = MaterialTheme.typography.bodyMedium)
+                        IconButton(onClick = { viewModel.removeNavItem(name) }) {
+                            Icon(Icons.Filled.Close, contentDescription = "Remove $label")
+                        }
+                    }
+                }
+
+                if (state.selectedNavItems.size < 5) {
+                    val available = viewModel.availableNavItems.filter { it.first !in state.selectedNavItems }
+                    if (available.isNotEmpty()) {
+                        var expanded by remember { mutableStateOf(false) }
+                        Box {
+                            OutlinedButton(onClick = { expanded = true }) {
+                                Icon(Icons.Filled.Add, contentDescription = null)
+                                Spacer(Modifier.size(4.dp))
+                                Text("Add Item")
+                            }
+                            DropdownMenu(expanded = expanded, onDismissRequest = { expanded = false }) {
+                                available.forEach { (name, label) ->
+                                    DropdownMenuItem(
+                                        text = { Text(label) },
+                                        onClick = {
+                                            viewModel.addNavItem(name)
+                                            expanded = false
+                                        },
+                                    )
+                                }
+                            }
+                        }
+                    }
+                } else {
+                    Text(
+                        text = "Maximum of 5 items",
+                        style = MaterialTheme.typography.bodySmall,
+                        color = MaterialTheme.colorScheme.onSurfaceVariant,
+                    )
+                }
+            }
+
             // Test result
             AnimatedVisibility(
                 visible = state.testResult != null,

app/src/main/java/com/m57/hermescontrol/ui/settings/SettingsViewModel.kt

@@ -22,6 +22,7 @@ data class SettingsUiState(
     val isTesting: Boolean = false,
     val testResult: String? = null,
     val isSaved: Boolean = false,
+    val selectedNavItems: List<String> = emptyList(),
 )
 
 class SettingsViewModel : ViewModel() {
@@ -43,6 +44,7 @@ class SettingsViewModel : ViewModel() {
                 // choice from persistent storage on init. Previously this slot
                 // was missing — always defaulted to ThemePreference.SYSTEM.
                 themePreference = AuthManager.getThemePreference(),
+                selectedNavItems = AuthManager.getBottomNavItems(),
             )
         }
     }
@@ -67,6 +69,52 @@ class SettingsViewModel : ViewModel() {
         _uiState.update { it.copy(themePreference = theme, isSaved = false) }
     }
 
+    /** All screens available for bottom-nav selection (name → display label). */
+    val availableNavItems: List<Pair<String, String>> =
+        listOf(
+            "ChatScreen" to "Chat",
+            "SkillsScreen" to "Skills",
+            "CronJobsScreen" to "Cron Jobs",
+            "SystemScreen" to "System",
+            "SettingsScreen" to "Settings",
+            "ProfilesScreen" to "Profiles",
+            "WebhooksScreen" to "Webhooks",
+            "GatewayScreen" to "Gateway",
+            "ToolsetsScreen" to "Toolsets",
+            "PluginsScreen" to "Plugins",
+            "ConfigScreen" to "Config",
+            "McpServersScreen" to "MCP Servers",
+            "ModelScreen" to "Models",
+            "PairingScreen" to "Pairing",
+            "KeysScreen" to "Keys",
+            "ChannelsScreen" to "Channels",
+            "LogsScreen" to "Logs",
+            "KanbanScreen" to "Kanban",
+            "AchievementsScreen" to "Achievements",
+        )
+
+    /** Add a nav item to the bottom bar (max 5). Auto-saves. */
+    fun addNavItem(name: String) {
+        val current = _uiState.value.selectedNavItems
+        if (name in current || current.size >= 5) return
+        val updated = current + name
+        _uiState.update { it.copy(selectedNavItems = updated) }
+        AuthManager.setBottomNavItems(updated)
+    }
+
+    /** Remove a nav item from the bottom bar. Auto-saves. */
+    fun removeNavItem(name: String) {
+        val updated = _uiState.value.selectedNavItems - name
+        _uiState.update { it.copy(selectedNavItems = updated) }
+        AuthManager.setBottomNavItems(updated)
+    }
+
+    /** Reorder the selected nav items. Auto-saves. */
+    fun reorderNavItems(items: List<String>) {
+        _uiState.update { it.copy(selectedNavItems = items) }
+        AuthManager.setBottomNavItems(items)
+    }
+
     fun save() {
         val state = _uiState.value
         val port = state.port.toIntOrNull() ?: 9119