Update backend models, controllers, and session

src/settings.py

@@ -1,7 +1,6 @@
 import json
-import wifi
-import ubinascii
-import machine
+import os
+import binascii
 
 class Settings(dict):
     SETTINGS_FILE = "/settings.json"
@@ -10,8 +9,30 @@ class Settings(dict):
         super().__init__()
         self.load()  # Load settings from file during initialization
 
+    def generate_secret_key(self):
+        """Generate a random secret key for session signing."""
+        try:
+            # Try to use os.urandom for secure random bytes
+            random_bytes = os.urandom(32)
+            return binascii.hexlify(random_bytes).decode('utf-8')
+        except (AttributeError, NotImplementedError):
+            # Fallback for MicroPython or systems without os.urandom
+            try:
+                import secrets
+                return secrets.token_hex(32)
+            except ImportError:
+                # Last resort: use a combination of time and random
+                import time
+                import random
+                random.seed(time.time())
+                return binascii.hexlify(bytes([random.randint(0, 255) for _ in range(32)])).decode('utf-8')
+
     def set_defaults(self):
-        self = {}
+        """Set default settings if they don't exist."""
+        if 'session_secret_key' not in self:
+            self['session_secret_key'] = self.generate_secret_key()
+            # Save immediately when generating a new key
+            self.save()
 
     def save(self):
         try:
@@ -23,12 +44,19 @@ class Settings(dict):
             print(f"Error saving settings: {e}")
 
     def load(self):
+        loaded_from_file = False
         try:
             with open(self.SETTINGS_FILE, 'r') as file:
                 loaded_settings = json.load(file)
             self.update(loaded_settings)
+            loaded_from_file = True
             print("Settings loaded successfully.")
         except Exception as e:
             print(f"Error loading settings")
+            self.clear()
+        finally:
+            # Ensure defaults are set even if file exists but is missing keys
             self.set_defaults()
-            self.save()
+            # Only save if file didn't exist or was invalid
+            if not loaded_from_file:
+                self.save()