feat: resize images to max 1920px before upload

Add expo-image-manipulator. In pickImage(), detect if image dimensions
exceed 1920px and resize (keeping aspect ratio) + compress to JPEG 0.85.
Previously only JPEG quality was set but dimensions were untouched.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

artifacts/postiz-mobile/app/(tabs)/compose.tsx

@@ -4,6 +4,7 @@ import DateTimePicker from "@react-native-community/datetimepicker";
 import AsyncStorage from "@react-native-async-storage/async-storage";
 import * as Haptics from "expo-haptics";
 import { Image } from "expo-image";
+import * as ImageManipulator from "expo-image-manipulator";
 import * as ImagePicker from "expo-image-picker";
 import { fetch as expoFetch } from "expo/fetch";
 import { useLocalSearchParams } from "expo-router";
@@ -146,10 +147,25 @@ export default function ComposeScreen() {
     const result = await ImagePicker.launchImageLibraryAsync({
       mediaTypes: ["images"],
       allowsEditing: false,
-      quality: 0.85,
+      quality: 1,
     });
     if (!result.canceled && result.assets[0]) {
-      setImageUri(result.assets[0].uri);
+      const asset = result.assets[0];
+      const MAX_DIM = 1920;
+      const w = asset.width ?? 0;
+      const h = asset.height ?? 0;
+      const needsResize = w > MAX_DIM || h > MAX_DIM;
+      if (needsResize) {
+        const landscape = w >= h;
+        const resized = await ImageManipulator.manipulateAsync(
+          asset.uri,
+          [{ resize: landscape ? { width: MAX_DIM } : { height: MAX_DIM } }],
+          { compress: 0.85, format: ImageManipulator.SaveFormat.JPEG }
+        );
+        setImageUri(resized.uri);
+      } else {
+        setImageUri(asset.uri);
+      }
       setExistingMedia([]);
     }
   };

artifacts/postiz-mobile/package.json

@@ -33,6 +33,7 @@
     "expo-glass-effect": "~0.1.4",
     "expo-haptics": "~15.0.8",
     "expo-image": "~3.0.11",
+    "expo-image-manipulator": "~13.0.6",
     "expo-image-picker": "~17.0.9",
     "expo-linear-gradient": "~15.0.8",
     "expo-linking": "~8.0.10",