Add experimental e-ink display section to hardware docs

Documents e-ink options for testing:
- Modos Paper (75Hz, open-source FPGA) - ships Jan 2026
- DASUNG Paperlike 253 (33Hz, frontlight)
- Waveshare development boards
- Industrial/outdoor options (SEEKINK, Geniatech)

Includes honest assessment of trade-offs and recommended
use cases (outdoor, solar-powered, idle signage).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/hardware/hardware-recommendations.md

@@ -281,6 +281,91 @@ github.com/fujitsu-atm/f53-python
 - VESA mount compatible
 - USB touch, HDMI video
 
+### Experimental: E-Ink Displays
+
+> [!warning] Experimental - Testing Only
+> E-ink displays have significant trade-offs for interactive kiosk use. Document for evaluation purposes.
+
+**Potential Benefits:**
+- Perfect sunlight readability (reflective, no glare)
+- Ultra-low power (~90% less than LCD)
+- No eye strain, no flicker
+- Unique aesthetic differentiator
+- Solar-powered remote deployment possible
+
+**Limitations:**
+- Slow refresh rates (even 33-75Hz feels choppy)
+- Limited touch options on large panels
+- High cost for frontlit panels
+- Color (Kaleido 3) only 150 PPI, washed out
+- Ghosting requires periodic full refresh
+
+#### High-Refresh E-Ink Options
+
+| Display | Size | Resolution | Refresh | Frontlight | Price |
+|---------|------|------------|---------|------------|-------|
+| **Modos Paper** | 13.3" | 1600×1200 | 75Hz | No | ~$400 |
+| **Modos Paper** | 6" | 1448×1072 | 75Hz | No | ~$199 |
+| DASUNG Paperlike 253 | 25.3" | 3200×1800 | 33Hz | Yes | ~$2,250 |
+| DASUNG Paperlike Color | 25.3" | Kaleido 3 | ~15Hz | Yes | ~$3,000+ |
+
+#### Open Source: Modos Paper Monitor
+
+> [!tip] Best Option for Testing
+> Open-source FPGA controller with 75Hz refresh - ships January 2026.
+
+- **Repository:** github.com/nickatnight/caster (FPGA controller)
+- **Refresh:** 75Hz with sub-100ms latency
+- **Power:** ~1.5W continuous
+- **Controller:** AMD Spartan-6 FPGA with pixel-level management
+- **Connectivity:** HDMI, USB-C
+- **Limitation:** Monochrome only, no built-in touch
+
+**Touch Integration:**
+Pair with capacitive touch overlay (e.g., ILITEK controller) for touch input.
+
+#### Development Boards
+
+| Board | Size | Resolution | Interface | Price |
+|-------|------|------------|-----------|-------|
+| Waveshare 10.3" HAT | 10.3" | 1872×1404 | SPI/USB | ~$200 |
+| Waveshare 7.8" HAT | 7.8" | 1872×1404 | SPI | ~$120 |
+| GooDisplay GDEY042T81 | 4.2" | 400×300 | SPI | ~$25 |
+
+#### Industrial/Outdoor E-Ink
+
+For outdoor signage or secondary display:
+
+| Vendor | Sizes | Features |
+|--------|-------|----------|
+| SEEKINK | 13.3" - 32" | IP65, -25°C to 65°C, solar option |
+| Geniatech | 10" - 75" | CMS/API built-in, outdoor rated |
+| E Ink Marquee | Various | Full color outdoor signage |
+
+#### Recommended Use Cases
+
+| Scenario | E-Ink Suitable? | Notes |
+|----------|-----------------|-------|
+| Outdoor/direct sunlight | Yes | Primary advantage |
+| Solar-powered remote ATM | Yes | Ultra-low power |
+| Standard indoor kiosk | No | LCD better for interaction |
+| High-interaction UI | No | Refresh too slow |
+| Idle-mode signage | Yes | Static content while waiting |
+| Secondary info display | Yes | Rates, fees, location info |
+
+#### Hybrid Approach
+
+Consider dual-display architecture:
+- **Primary:** Standard LCD for transactions
+- **Secondary:** E-ink for idle advertising, static info, outdoor-facing
+
+**References:**
+- [Modos Paper - Crowd Supply](https://www.crowdsupply.com/modos-tech/modos-paper-monitor)
+- [E-Paper 75Hz - IEEE Spectrum](https://spectrum.ieee.org/e-paper-display-modos)
+- [DASUNG Paperlike 253](https://shop.dasung.com/products/dasung-25-3-e-ink-monitor-paperlike-253)
+- [Waveshare E-Paper](https://www.waveshare.com/product/raspberry-pi/displays/e-paper.htm)
+- [SEEKINK Outdoor](https://www.seekink.com/outdoor-e-ink-display/)
+
 ---
 
 ## Thermal Printers