Refine repository structure for KiCad 9 optimization

- Add dedicated /kicad/ directory with organized subdirectories for libraries, schematics, gerbers, plots, and backups
- Create comprehensive KiCad 9 library structure (symbols, footprints, 3D models)
- Add manufacturing-ready directories for production files (gerbers, drill, pick-and-place)
- Update all README files with KiCad-specific documentation and workflows
- Add KiCad-optimized .gitignore file for proper version control
- Create KICAD-PROJECT-TEMPLATE.md comprehensive usage guide
- Add hardware assembly documentation and BOM management
- Include detailed manufacturing file generation instructions
- Add docs structure with design-notes and user-manual directories
- Provide complete workflow from design to manufacturing with quality checklists

kicad/libraries/3dmodels/README.md

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+# /kicad/libraries/3dmodels
+
+Custom 3D models for your KiCad project footprints.
+
+## File Formats
+- **STEP files (`.step`)**: Preferred for mechanical accuracy and CAD integration
+- **VRML files (`.wrl`)**: Legacy format, still supported by KiCad 3D viewer
+- **WRL files (`.wrl`)**: Alternative VRML extension
+
+## Naming Convention
+- Use descriptive names matching your footprints
+- Examples:
+  - `USB-C_Receptacle.step`
+  - `STM32F4_LQFP64.step`
+  - `Header_2x10_2.54mm.wrl`
+
+## Model Guidelines
+- **Scale**: Ensure models are in millimeters (KiCad's native unit)
+- **Origin**: Position the model origin to match the footprint's origin
+- **Orientation**: Align the model with the footprint's orientation
+- **Detail Level**: Balance detail with file size for performance
+
+## File Organization
+```
+3dmodels/
+├── connectors/
+│   ├── USB-C_Receptacle.step
+│   ├── Header_2x10_2.54mm.step
+│   └── Terminal_Block_3pin.step
+├── mcu/
+│   ├── STM32F4_LQFP64.step
+│   └── ESP32_Module.step
+├── sensors/
+│   ├── BME280_LGA8.step
+│   └── MPU6050_QFN24.step
+└── passive/
+    ├── Resistor_0603.step
+    ├── Capacitor_0805.step
+    └── LED_0603.step
+```
+
+## Associating Models with Footprints
+1. Open footprint in KiCad Footprint Editor
+2. Go to **Footprint Properties**
+3. Click **3D Settings** tab
+4. Add 3D model path (use relative paths)
+5. Adjust offset, rotation, and scale if needed
+
+## Model Sources
+- **Manufacturer websites**: Often provide STEP models
+- **Component distributors**: Digi-Key, Mouser, etc.
+- **3D model libraries**: GrabCAD, 3D ContentCentral
+- **KiCad official libraries**: For standard components
+- **Custom modeling**: Create your own in CAD software
+
+## Best Practices
+- Use relative paths: `${KIPRJMOD}/kicad/libraries/3dmodels/`
+- Keep file sizes reasonable (< 1MB per model when possible)
+- Test models in KiCad 3D viewer before finalizing
+- Document model sources and modifications
+- Version control important custom models

kicad/libraries/README.md

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+# /kicad/libraries
+
+Custom KiCad libraries for your project.
+
+## Directory Structure
+
+- `symbols/` - Custom schematic symbols (`.kicad_sym` files)
+- `footprints/` - Custom footprints (`.pretty` directories)
+- `3dmodels/` - Custom 3D models (`.step`, `.wrl` files)
+
+## Usage Guidelines
+
+### Symbols (`symbols/`)
+- Store custom schematic symbols as `.kicad_sym` files
+- Use descriptive names (e.g., `MyProject_MCU.kicad_sym`)
+- Include symbol properties and documentation
+
+### Footprints (`footprints/`)
+- Each footprint library is a `.pretty` directory
+- Store related footprints together (e.g., `MyProject_Connectors.pretty/`)
+- Include courtyard and fabrication layers
+
+### 3D Models (`3dmodels/`)
+- Store STEP files (`.step`) for mechanical accuracy
+- Store VRML files (`.wrl`) for KiCad 3D viewer compatibility
+- Use consistent naming with footprints
+
+## Library Configuration
+
+1. In KiCad, go to **Preferences → Manage Symbol Libraries**
+2. Add your custom symbol libraries from `symbols/`
+3. Go to **Preferences → Manage Footprint Libraries**
+4. Add your custom footprint libraries from `footprints/`
+5. Configure 3D model paths to point to `3dmodels/`
+
+## Best Practices
+
+- Use relative paths in your project settings
+- Document custom components in `/hardware/datasheets/`
+- Version control all custom libraries
+- Follow KiCad naming conventions

kicad/libraries/footprints/README.md

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+# /kicad/libraries/footprints
+
+Custom footprints for your KiCad project.
+
+## File Format
+- Footprints are stored in `.pretty` directories
+- Each `.pretty` directory is a footprint library
+- Individual footprints are `.kicad_mod` files within the `.pretty` directory
+
+## Naming Convention
+- Library directories: `ProjectName_ComponentType.pretty`
+- Footprint files: `ComponentName.kicad_mod`
+- Examples:
+  - `MyProject_Connectors.pretty/`
+    - `USB-C_Receptacle.kicad_mod`
+    - `Header_2x10_2.54mm.kicad_mod`
+  - `MyProject_MCU.pretty/`
+    - `STM32F4_LQFP64.kicad_mod`
+
+## Footprint Creation Guidelines
+- Include proper pad sizes and drill holes
+- Add courtyard layer (F.CrtYd/B.CrtYd) with 0.25mm clearance minimum
+- Include fabrication layer (F.Fab/B.Fab) with component outline
+- Add silkscreen layer (F.SilkS/B.SilkS) for component identification
+- Set reference designator and value positions
+- Include 3D model associations when available
+
+## Layer Guidelines
+- **F.Cu/B.Cu**: Copper pads and traces
+- **F.SilkS/B.SilkS**: Silkscreen printing
+- **F.Fab/B.Fab**: Fabrication layer (component outline)
+- **F.CrtYd/B.CrtYd**: Courtyard (component keepout area)
+- **F.Mask/B.Mask**: Solder mask openings
+
+## Adding to Project
+1. Open KiCad Project Manager
+2. Go to **Preferences → Manage Footprint Libraries**
+3. Click **Add** and browse to this directory
+4. Select your `.pretty` directory
+5. Set library nickname and path (use relative paths)
+
+## Example Library Structure
+```
+footprints/
+├── MyProject_Connectors.pretty/
+│   ├── USB-C_Receptacle.kicad_mod
+│   ├── Header_2x10_2.54mm.kicad_mod
+│   └── Terminal_Block_3pin.kicad_mod
+├── MyProject_MCU.pretty/
+│   ├── STM32F4_LQFP64.kicad_mod
+│   └── ESP32_Module.kicad_mod
+└── MyProject_Sensors.pretty/
+    ├── BME280_LGA8.kicad_mod
+    └── MPU6050_QFN24.kicad_mod

kicad/libraries/symbols/README.md

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+# /kicad/libraries/symbols
+
+Custom schematic symbols for your KiCad project.
+
+## File Format
+- Store symbols as `.kicad_sym` files
+- Each file can contain multiple related symbols
+
+## Naming Convention
+- Use descriptive names: `ProjectName_ComponentType.kicad_sym`
+- Examples:
+  - `MyProject_MCU.kicad_sym`
+  - `MyProject_Connectors.kicad_sym`
+  - `MyProject_PowerManagement.kicad_sym`
+
+## Symbol Creation Guidelines
+- Include all necessary pins with proper electrical types
+- Add symbol properties (Reference, Value, Footprint, Datasheet)
+- Use standard KiCad symbol conventions
+- Include documentation strings
+- Set appropriate pin numbers and names
+
+## Adding to Project
+1. Open KiCad Project Manager
+2. Go to **Preferences → Manage Symbol Libraries**
+3. Click **Add** and browse to this directory
+4. Select your `.kicad_sym` file
+5. Set library nickname and path (use relative paths)
+
+## Example Library Structure
+```
+symbols/
+├── MyProject_MCU.kicad_sym          # Microcontrollers
+├── MyProject_Connectors.kicad_sym   # Custom connectors
+├── MyProject_Sensors.kicad_sym      # Sensor symbols
+└── MyProject_Power.kicad_sym        # Power management ICs