feat: add user avatar functionality and update related routes

- Implemented avatar upload and deletion in the Auth context.
- Updated UserProfile component to handle avatar display and actions.
- Modified backend routes to return anonymous user ID when auth is disabled.
- Added avatar_url column to users table in the database.
- Enhanced UI for user menu and profile modal to support avatar display.
- Updated translations for new avatar-related strings.
- Improved stock status calculation for medications in the planner.

frontend/src/i18n/de.json

@@ -259,7 +259,15 @@
     "passwordReset": "Passwort zurückgesetzt",
     "passwordResetSuccess": "Ihr Passwort wurde zurückgesetzt. Weiterleitung zur Anmeldung...",
     "profileUpdated": "Profil erfolgreich aktualisiert",
-    "rememberMe": "Angemeldet bleiben"
+    "rememberMe": "Angemeldet bleiben",
+    "localAccount": "Lokales Konto",
+    "updatePassword": "Passwort ändern",
+    "fillAllFields": "Bitte alle Passwortfelder ausfüllen",
+    "signOut": "Abmelden",
+    "uploadAvatar": "Avatar hochladen",
+    "removeAvatar": "Avatar entfernen",
+    "avatarUpdated": "Avatar aktualisiert",
+    "avatarRemoved": "Avatar entfernt"
   },
   "common": {
     "loading": "Wird geladen...",

frontend/src/i18n/en.json

@@ -261,7 +261,15 @@
     "passwordReset": "Password Reset",
     "passwordResetSuccess": "Your password has been reset. Redirecting to login...",
     "profileUpdated": "Profile updated successfully",
-    "rememberMe": "Remember me"
+    "rememberMe": "Remember me",
+    "localAccount": "Local Account",
+    "updatePassword": "Update Password",
+    "fillAllFields": "Please fill in all password fields",
+    "signOut": "Sign Out",
+    "uploadAvatar": "Upload avatar",
+    "removeAvatar": "Remove avatar",
+    "avatarUpdated": "Avatar updated",
+    "avatarRemoved": "Avatar removed"
   },
   "common": {
     "loading": "Loading...",