feat: merge display-fix — touch driver, keyboard, WiFi setup UI

Squash-merge of feature/display-fix (27 commits):
- AXS15231B touch driver with coordinate parsing (touch.c/h)
- On-screen keyboard with layout/hit detection (keyboard.c/h)
- WiFi setup state machine + config_add_wifi (wifi_setup.c/h)
- Web-based WiFi setup via captive portal
- Display rotation fix (stride=480), color fixes, DMA byte-swap
- WiFi QR code on BOOT and ERROR screens
- ERROR state transition after WiFi retries exhausted
- Unit tests: test_touch, test_keyboard, test_wifi_setup
- Integration test: wifi_setup.mjs
- E2E test: wifi-setup.spec.mjs
- Per-board hardware locks for flash targets

Conflicts resolved: took master for config/cvm/api/main (more current),
took display-fix for display/axs15231b (newer fixes).

1 files changed, 165 insertions, 0 deletions

diff --git a/DISPLAY_UI_PLAN.md b/DISPLAY_UI_PLAN.md
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+# TollGate Display UI Design
+
+## Display Hardware
+- **Panel:** 3.5" IPS, 320x480 portrait (AXS15231B QSPI)
+- **Font:** 8x8 bitmap, scalable (1x=8px, 2x=16px, 3x=24px)
+- **Capabilities:** Text rendering, QR codes, filled rectangles
+- **No touch input** — display is output-only signage
+
+## Color Palette
+
+| Color | RGB565 | Usage |
+|-------|--------|-------|
+| Black | `0x0000` | Background |
+| White | `0xFFFF` | Primary text |
+| Cyan | `0x07FF` | Titles, labels |
+| Yellow | `0xFFE0` | Price, warnings |
+| Green | `0x07E0` | Success, wallet OK |
+| Orange | `0xFD20` | Accent (Bitcoin orange) |
+| Red | `0xF800` | Errors, alerts |
+| Dim gray | `0x8410` | Secondary info |
+
+## Screen States
+
+### 1. BOOT
+Shown during startup until WiFi connects and services start.
+
+```
+┌──────────────────────────┐
+│        TollGate          │  cyan, scale 2
+│      connecting...       │  yellow, scale 1
+│    WiFi: trying...       │  dim, scale 1
+└──────────────────────────┘
+```
+
+### 2. READY — QR Cycling
+Cycles every 5 seconds between WiFi QR and Portal QR.
+
+**View A — WiFi QR:**
+```
+┌──────────────────────────┐
+│         ┌──────┐         │
+│         │  QR  │         │  WIFI:S:<ssid>;T:nopass;;
+│         └──────┘         │
+│   Scan to connect        │  cyan
+│   SSID: TollGate-XXXX   │  white
+│   21 sats/min            │  orange
+│   Wallet: 420 sats       │  green/yellow/red
+└──────────────────────────┘
+```
+
+**View B — Portal QR:**
+```
+┌──────────────────────────┐
+│         ┌──────┐         │
+│         │  QR  │         │  http://10.x.x.x/
+│         └──────┘         │
+│   Portal URL             │  cyan
+│   Mint: testnut...       │  orange
+│   21 sats/min            │  orange
+│   Clients: 3             │  green
+└──────────────────────────┘
+```
+
+### 3. PAYMENT_RECEIVED
+Shows for 3 seconds after payment, then returns to READY.
+
+```
+┌──────────────────────────┐
+│   ████████████████████   │  green bar
+│      ACCESS GRANTED      │  white on green, scale 2
+│   ████████████████████   │
+│      Paid: 42 sats       │  white
+│      Time: 2 min         │  white
+│   Wallet: 462 sats       │  green
+└──────────────────────────┘
+```
+
+### 4. ERROR
+Shown when upstream WiFi is disconnected.
+
+```
+┌──────────────────────────┐
+│   ████████████████████   │  red bar
+│     NO UPSTREAM          │  white on red, scale 2
+│   ████████████████████   │
+│   Internet unavailable   │  white
+│   Check WiFi config      │  yellow
+│   AP still active        │  green
+│   SSID: TollGate-XXXX   │  dim
+└──────────────────────────┘
+```
+
+## State Synchronization
+
+### Data sources and update triggers
+
+| Display data | Source function | Update trigger |
+|-------------|----------------|----------------|
+| SSID | `config.ap_ssid` | Once at `start_services()` |
+| Portal URL | `config.ap_ip_str` | Once at `start_services()` |
+| Mint URL | `config.mint_url` | Once at `start_services()` |
+| Price | `config.price_per_step` | Once at `start_services()` |
+| **Wallet balance** | `nucula_wallet_balance()` | **Every 5s in main loop** |
+| **Client count** | `session_active_count()` | **Every 5s in main loop + AP events** |
+| **Last payment** | `display_notify_payment()` | **On each payment in API handler** |
+| WiFi status | Event handler | On STA connect/disconnect |
+
+### State transitions
+
+```
+app_main()
+  └─ display_set_state(BOOT)
+  └─ display_update(price, mint, ssid)   ← config data available after config_init
+
+wifi_event_handler(STA_DISCONNECTED)
+  └─ display_set_state(ERROR)
+  └─ display_update(wifi_status="retrying...")
+
+ip_event_handler(STA_GOT_IP)
+  └─ start_services()
+       └─ display_set_state(READY)
+       └─ display_update(ssid, portal_url, mint, price)
+
+tollgate_api (POST / payment)
+  └─ session_create()
+  └─ nucula_wallet_receive()
+  └─ display_notify_payment(amount_sats, allotment)   ← NEW
+  └─ display_set_state(PAYMENT_RECEIVED)
+
+display_task (3s timeout)
+  └─ auto-return PAYMENT_RECEIVED → READY
+
+app_main() main loop (every 5s)
+  └─ display_update(wallet_balance, client_count)     ← NEW periodic refresh
+```
+
+### New API: `display_notify_payment()`
+
+```c
+void display_notify_payment(int amount_sats, int64_t allotment_ms);
+```
+
+Stores the last payment amount and time purchased for the PAYMENT screen to display.
+
+## Implementation Checklist
+
+### Done
+- [x] QSPI driver working with correct colors (DMA byte-swap + RAMWR)
+- [x] BOOT screen with title and WiFi status
+- [x] READY screen with QR cycling, price, mint, balance, clients
+- [x] PAYMENT screen layout (green banner, amount, time, wallet)
+- [x] ERROR screen layout (red banner, guidance, AP status)
+- [x] WiFi disconnect → ERROR state transition
+- [x] WiFi connect → READY state transition
+
+### TODO — State Sync
+- [ ] Periodic display data refresh in main loop (wallet balance, client count every 5s)
+- [ ] `display_notify_payment()` API to pass payment amount and allotment
+- [ ] Call `display_set_state(PAYMENT_RECEIVED)` from tollgate_api.c after payment
+- [ ] Pass config data (price, mint) to display during boot phase
+- [ ] Update client count on AP station connect/disconnect events
+
+### TODO — Polish
+- [ ] Run `make test-unit` to check for regressions
+- [ ] Commit, push, prepare for merge