Update watch face: modular refactor + OWM/Solar/background + codegen tools

- Split render into FieldTable/Fields/Icons/Layout/Settings modules
- Add Fenix8V3Background, Owm (weather), Solar modules
- Add tools/ generators (gen_fields/gen_icons/gen_themes/gen_preview_svg)
- Tune README/manifest/strings/settings

tools/gen_preview_svg.py

@@ -1,10 +1,11 @@
 #!/usr/bin/env python3
-"""Render preview-themes.svg and preview.html by replaying the face's draw calls.
+"""重放表盘自己的绘制逻辑，产出 preview-themes.svg 和 preview.html。
 
-Colours are parsed straight out of source/Themes.mc and the geometry constants
-are the same literals as source/Fenix8V3View.mc, so the preview cannot drift
-from the firmware.  Text is drawn with a web font rather than Garmin's Roboto
-Condensed / Bionic, so judge geometry and colour here, not glyph shapes.
+颜色直接解析自 source/Themes.mc，几何常量与 source/Fenix8V3View.mc /
+source/Layout.mc 保持同一套字面值，所以预览不会和固件漂移。
+
+⚠️ 文字用的是网页字体，真机是 Garmin 内置的 Roboto / Bionic，字形会有差异。
+**几何和配色可信，字形不可信** —— 判断字形要看模拟器截图。
 
     python3 tools/gen_preview_svg.py
 """