docs: align README to standardized 8-section layout and add dual-render assets

docs/images/README.md

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+# Hardware Images Manifest
+
+`hero.png` — Transparent background cut-out of the ESP32 aquarium feeder controller, DS18B20 temperature probe, and MOSFET motor driver circuit layout for theme-agnostic README rendering.
+
+`hero-site.webp` — Portfolio dark-canvas render (1600×1000px, `#0b0d10` canvas with left gradient fade and `#8ecbff` rim light) for the portfolio resume site.