adding folder structure and READMEs

hardware/README.md

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+# /hardware
+
+Electrical design files including schematics, PCB layout, BOM, and simulations.

hardware/bom/README.md

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+# /hardware/bom
+
+Bill of Materials in CSV or spreadsheet format.

hardware/manufacturing/README.md

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+# /hardware/manufacturing
+
+Gerbers, pick-and-place files, and drill files.

hardware/pcb/README.md

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+# /hardware/pcb
+
+PCB layout design files.

hardware/schematics/README.md

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+# /hardware/schematics
+
+KiCad or other EDA schematic files.

hardware/simulations/README.md

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+# /hardware/simulations
+
+Simulation files for circuit behavior (e.g., SPICE).