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/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