docs: add standardized 8-section README, dual-render images, and image manifest

docs/images/README.md

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+# Hardware Images Manifest
+
+`hero.png` — Transparent background cut-out of the ESP32 Wi-Fi MQTT bridge controller, RA-01 LoRa radio module, and solenoid water valve control 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.