feat: setup app navigation and tabs

frontend/src/app/_layout.tsx

@@ -1,15 +1,64 @@
-import { DarkTheme, DefaultTheme, ThemeProvider } from 'expo-router';
-import { useColorScheme } from 'react-native';
+import { Tabs } from "expo-router";
+import { Ionicons } from "@expo/vector-icons";
 
-import { AnimatedSplashOverlay } from '@/components/animated-icon';
-import AppTabs from '@/components/app-tabs';
-
-export default function TabLayout() {
-  const colorScheme = useColorScheme();
+export default function Layout() {
   return (
-    <ThemeProvider value={colorScheme === 'dark' ? DarkTheme : DefaultTheme}>
-      <AnimatedSplashOverlay />
-      <AppTabs />
-    </ThemeProvider>
+    <Tabs
+      screenOptions={{
+        headerShown: false,
+
+        tabBarActiveTintColor: "#0E8A61",
+        tabBarInactiveTintColor: "#9CA3AF",
+
+        tabBarStyle: {
+          height: 70,
+          paddingBottom: 10,
+          paddingTop: 10,
+          backgroundColor: "#FFFFFF",
+          borderTopWidth: 0,
+          elevation: 8,
+        },
+      }}
+    >
+      <Tabs.Screen
+        name="index"
+        options={{
+          title: "Inicio",
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="home-outline" size={size} color={color} />
+          ),
+        }}
+      />
+
+      <Tabs.Screen
+        name="alerts"
+        options={{
+          title: "Alertas",
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="notifications-outline" size={size} color={color} />
+          ),
+        }}
+      />
+
+      <Tabs.Screen
+        name="guide"
+        options={{
+          title: "Guía",
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="leaf-outline" size={size} color={color} />
+          ),
+        }}
+      />
+
+      <Tabs.Screen
+        name="profile"
+        options={{
+          title: "Perfil",
+          tabBarIcon: ({ color, size }) => (
+            <Ionicons name="person-outline" size={size} color={color} />
+          ),
+        }}
+      />
+    </Tabs>
   );
 }

frontend/src/app/alerts.tsx

@@ -0,0 +1,15 @@
+import { View, Text } from "react-native";
+
+export default function AlertsScreen() {
+    return (
+        <View
+            style={{
+                flex: 1,
+                justifyContent: "center",
+                alignItems: "center",
+            }}
+        >
+        <Text>Alertas</Text>
+        </View>
+    );
+}

frontend/src/app/guide.tsx

@@ -0,0 +1,15 @@
+import { View, Text } from "react-native";
+
+export default function GuideScreen() {
+    return (
+        <View
+            style={{
+                flex: 1,
+                justifyContent: "center",
+                alignItems: "center",
+            }}
+        >
+        <Text>Guía</Text>
+        </View>
+    );
+}

frontend/src/app/index.tsx

@@ -0,0 +1,15 @@
+import { View, Text } from "react-native";
+
+export default function HomeScreen() {
+  return (
+    <View
+      style={{
+        flex: 1,
+        justifyContent: "center",
+        alignItems: "center",
+      }}
+    >
+      <Text>Inicio</Text>
+    </View>
+  );
+}

frontend/src/app/profile.tsx

@@ -0,0 +1,15 @@
+import { View, Text } from "react-native";
+
+export default function ProfileScreen() {
+    return (
+        <View
+            style={{
+                    flex: 1,
+                    justifyContent: "center",
+                    alignItems: "center",
+                }}
+            >
+            <Text>Perfil</Text>
+        </View>
+    );
+}