feat: add navigation with tab bar and screen layouts

Expo Router file-based navigation with glass tab bar,
3 tabs (Créations, Explorer, Profil), Phosphor icons,
modal picker, and fade transitions.

app/(tabs)/_layout.tsx

@@ -0,0 +1,44 @@
+import { Tabs } from "expo-router";
+import { GlassTabBar } from "@/components/glass";
+import { House, Compass, UserCircle } from "phosphor-react-native";
+import type { ColorValue } from "react-native";
+
+export default function TabLayout() {
+  return (
+    <Tabs
+      tabBar={(props) => <GlassTabBar {...props} />}
+      screenOptions={{
+        headerShown: false,
+        tabBarStyle: { display: "none" },
+      }}
+    >
+      <Tabs.Screen
+        name="index"
+        options={{
+          title: "Créations",
+          tabBarIcon: ({ color, size }: { color: ColorValue; size: number }) => (
+            <House size={size} color={color as string} weight="light" />
+          ),
+        }}
+      />
+      <Tabs.Screen
+        name="explore"
+        options={{
+          title: "Explorer",
+          tabBarIcon: ({ color, size }: { color: ColorValue; size: number }) => (
+            <Compass size={size} color={color as string} weight="light" />
+          ),
+        }}
+      />
+      <Tabs.Screen
+        name="profile"
+        options={{
+          title: "Profil",
+          tabBarIcon: ({ color, size }: { color: ColorValue; size: number }) => (
+            <UserCircle size={size} color={color as string} weight="light" />
+          ),
+        }}
+      />
+    </Tabs>
+  );
+}