feat: file dispatch system, file-type icons, multi-instance notepad

- Add extension-based dispatch to driver.storage.filedispatch with typed
  union (variant record THandlerKind = hkMagic/hkExtension)
- Extract file-type icon constants and mapping to core.gfx.fileicons
- Add core.search utility (getFileExtension, fmtFileSize, sortStringArray)
- Generate PUA bitmap icon fonts (32/64/128px) from Font Awesome via
  gen_file_icons.py + compile_icons.sh toolchain
- Integrate file dispatch into file browser (double-click triggers dispatch)
- Register notepad as handler for text file extensions
- Fix init order in app.mgr (filedispatch.init before app inits)
- Refactor notepad from singleton to multi-instance (up to 8 windows)
  using instance array, findStateByWid, and LVGL user_data on msgboxes

Dockerfile

@@ -6,7 +6,7 @@ ENV DEBIAN_FRONTEND=noninteractive
 RUN dpkg --add-architecture i386
 RUN apt-get update && apt-get install -y \
 	curl dos2unix wget git make nasm binutils xorriso grub-pc-bin gcc gcc-multilib \
-	python3 python3-pip && \
+	python3 python3-pip python3-pil && \
 	apt-get clean my room
 
 RUN pip3 install --no-cache-dir --break-system-packages "mkdocs>=1.6,<2" mkdocs-material