feat: migrate to Google Photos Picker API and update related documentation due to normal library api being depricated (kept for added media from app)

ignorefiles/GOOGLE_OAUTH_SETUP.md

@@ -5,10 +5,11 @@
 2. Click **Select a project** → **New Project**
 3. Name it and click **Create**
 
-## Step 2: Enable the Photos Library API
+## Step 2: Enable the Photos Picker API
 1. Go to **APIs & Services** → **Library**
-2. Search for **Photos Library API** → **Enable** it
-3. ⚠️ This step is **required** — without it, all Photos API calls return 403
+2. Search for **Photos Picker API** → **Enable** it
+3. ⚠️ This step is **required** — without it, all Picker API calls fail
+4. (The old "Photos Library API" is deprecated and no longer works)
 
 ## Step 3: Configure the OAuth Consent Screen
 1. Go to **APIs & Services** → **OAuth consent screen**
@@ -19,13 +20,12 @@
    - **Developer contact**: your email
 4. **Scopes** → Add or Remove Scopes → add these:
    - `openid`
-   - `https://www.googleapis.com/auth/photoslibrary`
+   - `https://www.googleapis.com/auth/photospicker.mediaitems.readonly`
    - `https://www.googleapis.com/auth/userinfo.email`
    - `https://www.googleapis.com/auth/userinfo.profile`
 5. **Test users** → **Add your Google account email address**
    - ⚠️ This is **critical** — if your email is not listed as a test user,
-     Google will silently strip the Photos scope from the granted token,
-     causing a 403 "insufficient authentication scopes" error.
+     Google will silently strip the Photos Picker scope from the granted token.
 
 ## Step 4: Create an Android OAuth Client ID
 1. Go to **APIs & Services** → **Credentials**