3D PCB Design with Footprints

### Description
Create a complete **PCB layout with correct footprints and 3D component models** for the **FlightPanel-01 ATmega32U4 Button Panel** based on the existing schematic.

### Requirements
- ATmega32U4 (TQFP-44)
- CD74HC4067 multiplexer
- 8x toggle switches (via mux)
- 11x push buttons
- 1x rotary encoder with push button
- 3x potentiometers
- 4x LEDs with resistors

### Tasks
- Design a **2-layer PCB**
- Assign **correct footprints**
- Add **3D models for all components**
- Ensure clean routing and proper grounding
- Verify pin connections according to `PINOUT_REFERENCE.md`

### Deliverables
- PCB layout files
- 3D PCB model
- Gerber files
- BOM

### Goal
Produce a **manufacturing-ready PCB prototype**.

Start by locating the existing schematic and reading PINOUT_REFERENCE.md to confirm the ATmega32U4, multiplexer, switches, buttons, encoder, potentiometers, and LEDs. Create the specified two-layer layout with correct footprints, 3D models, routing, grounding, and the requested PCB, 3D model, Gerber, and BOM deliverables; verify the pin connections before considering it manufacturing-ready.

Written by the indexing model from the issue text.