Fix library GPS watermark anchor; use Cousine for Vietnamese glyphs

src/components/Viewfinder.tsx

@@ -100,7 +100,7 @@ export default function Viewfinder({
 
   const skiaImage = useImage(libraryImageUri || '');
   const customFont = useFont(
-    require('../../assets/CourierPrime-Regular.ttf'),
+    require('../../assets/Cousine-Regular.ttf'),
     Math.round(vw * 0.032)
   );
   // Monochrome Noto Emoji subset (📍 U+1F4CD, 📷 U+1F4F7) for the watermark
@@ -518,10 +518,24 @@ export default function Viewfinder({
     const pad = (n: number) => String(n).padStart(2, '0');
     const timestampStr = `${pad(d.getDate())}/${pad(d.getMonth() + 1)}/${d.getFullYear()} ${pad(d.getHours())}:${pad(d.getMinutes())}`;
 
-    // Baseline above the bottom chrome (shutter rail) so the watermark stays
-    // readable; polaroid frames push it further up onto the white area edge.
-    const yOffset = vh - (selectedFrame === 'polaroid' ? vh * 0.18 + 24 : 150);
-    const xOffset = selectedFrame === 'polaroid' ? vw * 0.08 : 16;
+    // Anchor to the PHOTO, not the screen. In camera mode the photo fills the
+    // screen (area = full canvas). In library mode the photo is contain-fitted
+    // with black letterbox — a screen-bottom baseline used to land below the
+    // photo on the letterbox, off the image, so users could not see it. Compute
+    // inside the fitted rect (imageFitRect) so the mark sits at the photo's
+    // bottom-left corner; keep it above the bottom chrome/shutter rail.
+    const area =
+      mode === 'library' && imageFitRect
+        ? imageFitRect
+        : { dx: 0, dy: 0, dw: vw, dh: vh };
+    const padBottom =
+      selectedFrame === 'polaroid' ? area.dh * 0.18 + 24 : Math.min(150, area.dh * 0.2);
+    const yOffset =
+      mode === 'library'
+        ? Math.min(area.dy + area.dh - padBottom, vh - 190) // never under the deck
+        : area.dy + area.dh - padBottom;
+    const xOffset =
+      area.dx + (selectedFrame === 'polaroid' ? area.dw * 0.08 : Math.min(16, area.dw * 0.04));
     const gap = (rect: { width?: number } | null) =>
       Math.round((rect?.width ?? Math.round(vw * 0.032)) + vw * 0.012);
     const pinW = iconFont.measureText('📍');

src/utils/exportEngine.ts

@@ -261,7 +261,7 @@ export async function processAndExportPhoto(
 
     // 8. Render GPS Geotag Watermark
     if (useGeotag && gpsInfo) {
-      const fontAsset = Asset.fromModule(require('../../assets/CourierPrime-Regular.ttf'));
+      const fontAsset = Asset.fromModule(require('../../assets/Cousine-Regular.ttf'));
       const iconFontAsset = Asset.fromModule(require('../../assets/NotoEmoji-GPS.ttf'));
       await Promise.all([fontAsset.downloadAsync(), iconFontAsset.downloadAsync()]);
       const [fontData, iconFontData] = await Promise.all([