Update docs

Author: ThomasFarstrike

docs/architecture/filesystem.md

@@ -6,14 +6,15 @@ MicroPythonOS uses a structured filesystem to organize apps, data, and resources
     - **com.micropythonos.helloworld/**: Installation directory for HelloWorld App. See [Creating Apps](../apps/creating-apps.md).
 - **builtin/**: Read-only filesystem compiled into the OS, mounted at boot by `main.py`.
     - **apps/**: See [Built-in Apps](../apps/built-in-apps.md).
-    - **res/mipmap-mdpi/default_icon_64x64.png**: Default icon for apps without one.
+    - **res/**: Resources (icons, fonts, etc.).
 - **lib/**: Libraries and frameworks
     - **mpos/**: MicroPythonOS libraries and frameworks
         - **ui/**: MicroPythonOS User Interface libraries and frameworks
-- **data/**: Storage for app data.
+- **prefs/**: Storage for app data.
     - **com.micropythonos.helloworld/**: App-specific storage (e.g., `config.json`)
     - **com.micropythonos.settings/**: Storage used by the built-in Settings App
     - **com.micropythonos.wifi/**: Storage used by the built-in WiFi App
-    - **images/**: Generic storage for images (use by e.g. the Camera App).
 
 This structure ensures a clear separation between system resources, apps, and user data.
+
+When creating packages, use `_` instead of `.` in names (e.g., `com_micropythonos_nostr`), since `.` has special meaning in Python module imports.