🔧 Fix persistent storage permission errors for HF Spaces

🚨 Critical Fix: Persistent storage now handles permission errors gracefully

✅ What's Fixed:
• Handle /data directory permission denied errors
• Graceful fallback to local backup strategy when persistent storage unavailable
• Better error logging with warning emojis
• App continues to function even without /data access

🔧 Technical Changes:
• Enhanced initialize_app() with proper permission error handling
• Updated _backup_to_persistent_storage() with try/catch for permissions
• Added conditional checks for persistent_db_path availability
• Better logging: ✅ success, ⚠️ warnings, 📁 local backup mode

📋 Result:
• App no longer crashes on HF Spaces with permission errors
• Still uses git + static file backup strategy
• Data persistence through multiple backup methods
• Graceful degradation when /data is inaccessible

Now works reliably in ANY environment!

app.py

@@ -424,12 +424,20 @@ def initialize_app():
         persistent_db_path = Path("/data/trees.db")
         local_db_path = Path("data/trees.db")
         
-        # Ensure both directories exist
-        persistent_db_path.parent.mkdir(parents=True, exist_ok=True)
+        # Ensure local directory exists
         local_db_path.parent.mkdir(parents=True, exist_ok=True)
         
-        # Check if we have a persistent database in /data
-        if persistent_db_path.exists():
+        # Try to ensure persistent directory exists (may fail on some systems)
+        try:
+            persistent_db_path.parent.mkdir(parents=True, exist_ok=True)
+            logger.info("✅ Persistent storage directory available at /data")
+        except (PermissionError, OSError) as e:
+            logger.warning(f"⚠️  Cannot create /data directory: {e}. Using local backup strategy.")
+            # Fallback to local backup strategy only
+            persistent_db_path = None
+        
+        # Check if we have a persistent database in /data (if available)
+        if persistent_db_path and persistent_db_path.exists():
             logger.info("Found persistent database, copying to local directory...")
             shutil.copy2(persistent_db_path, local_db_path)
             with sqlite3.connect(local_db_path) as conn:
@@ -449,7 +457,12 @@ def initialize_app():
                 if backup_path.exists():
                     logger.info(f"Found backup at {backup_path}, restoring...")
                     shutil.copy2(backup_path, local_db_path)
-                    shutil.copy2(backup_path, persistent_db_path)  # Also save to persistent storage
+                    # Try to save to persistent storage if available
+                    if persistent_db_path:
+                        try:
+                            shutil.copy2(backup_path, persistent_db_path)
+                        except (PermissionError, OSError):
+                            logger.warning("Cannot write to persistent storage")
                     backup_restored = True
                     break
             
@@ -463,8 +476,11 @@ def initialize_app():
         # Initialize database (creates tables if they don't exist)
         init_db()
         
-        # Initial backup to persistent storage
-        _backup_to_persistent_storage()
+        # Initial backup to persistent storage (if available)
+        if persistent_db_path:
+            _backup_to_persistent_storage()
+        else:
+            logger.info("📁 Using local backup strategy only (no persistent storage)")
         
         # Log current status
         if local_db_path.exists():
@@ -489,11 +505,15 @@ def _backup_to_persistent_storage():
         persistent_db = Path("/data/trees.db")
         
         if source_db.exists():
-            # Ensure /data directory exists
-            persistent_db.parent.mkdir(parents=True, exist_ok=True)
-            shutil.copy2(source_db, persistent_db)
-            logger.info(f"✅ Database backed up to persistent storage: {persistent_db}")
-            return True
+            # Try to ensure /data directory exists
+            try:
+                persistent_db.parent.mkdir(parents=True, exist_ok=True)
+                shutil.copy2(source_db, persistent_db)
+                logger.info(f"✅ Database backed up to persistent storage: {persistent_db}")
+                return True
+            except (PermissionError, OSError) as e:
+                logger.warning(f"⚠️  Cannot backup to persistent storage: {e}")
+                return False
     except Exception as e:
         logger.error(f"Persistent storage backup failed: {e}")
     return False