Docs: Full USB/NVMe boot coverage across all documentation

- build-guide.md: Boot medium options table, USB/NVMe flash instructions,
  EEPROM boot order setup, first-boot wizard boot config step
- user-manual.md: Required hardware lists all 3 boot targets, EEPROM
  bootstrap instructions, NVMe HAT recommendation for live use
- hardware-compatibility.md: New storage/boot media section with NVMe
  HAT compatibility table (official, Pimoroni, Geekworm)
- Obsidian wiki: Build section with all 3 targets + EEPROM config
- developer-guide.md: Added (from task completion)

docs/user-manual.md

@@ -26,10 +26,17 @@ live streaming.
 
 - Raspberry Pi 4 Model B (4GB+ RAM)
 - USB audio interface (class-compliant UAC2)
-- SD card (16GB+, Class A2 recommended) with mixer image flashed
+- Boot media (choose one):
+  - **SD card** (16GB+, Class A2) — good for dev/testing
+  - **USB SSD** via USB 3.0 — more reliable, but shares USB bus with audio
+  - **NVMe SSD + HAT** (PCIe) — **recommended for live use** — no bus contention
 - 5V/3A USB-C power supply
 - **Optional:** HDMI touchscreen, USB MIDI controller, Ethernet cable, USB camera
 
+> 💡 **Storage recommendation:** For live performances and recording, use an NVMe
+> HAT (official RPi, Pimoroni, or Geekworm) with a 128GB+ NVMe SSD. It uses
+> dedicated PCIe lanes and won't compete with your USB audio interface for bandwidth.
+
 ### Connections
 
 ```
@@ -64,8 +71,23 @@ Verified interfaces: see [docs/hardware-compatibility.md](hardware-compatibility
 
 ## 2. First Boot & Setup Wizard
 
-On first boot, the setup wizard runs automatically on the HDMI display.
+### Booting for the First Time
 
+1. Insert your boot media (SD, USB SSD, or NVMe) into the Pi
+2. Connect audio interface, MIDI controllers, and network
+3. Power on
+
+> ⚡ If booting from USB SSD or NVMe, the Pi's EEPROM must be configured to try
+> your boot device first. The setup wizard includes an EEPROM configuration step,
+> or you can configure it manually beforehand:
+> ```bash
+> sudo rpi-eeprom-config --edit
+> # USB boot:  BOOT_ORDER=0xf41
+> # NVMe boot: BOOT_ORDER=0xf614
+> ```
+
+On first boot, the **setup wizard** runs automatically on the HDMI display (or
+serial console). It walks through:
 ### Wizard Steps
 
 1. **Welcome screen** — language selection