Add PN532 toolkit firmware, web UI, and embedded SPIFFS assets

Includes ESP-IDF NFC stack (deep capture, 4K Classic geometry, UL write API,
open SoftAP), React dashboard with live tag diagnostics, and docs. README
updated for APIs and lab Wi-Fi defaults.

Made-with: Cursor

docs/WORKFLOWS.md

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+# Example workflows
+
+## 1. Read a MIFARE Classic sector
+
+1. Dashboard → **Poll once** to verify presence and UID.
+2. **Read** tab → enter default key (e.g. `FFFFFFFFFFFF`), block number, **MIFARE read block**.
+3. Copy hex → save to **Library** (local browser).
+
+## 2. Write a known-good block
+
+1. Authenticate with a key that still allows write on that sector.
+2. **Write** tab → paste **32 hex chars** (16 bytes) → confirm dialog.
+3. Re-read the block to verify.
+
+## 3. Ultralight / NTAG pages
+
+1. Use **Read** → **Ultralight read page** with page index (start at `0` for UID/lock pages per datasheet — exercise caution on OTP/lock bytes).
+
+## 4. Raw PN532 frames
+
+1. **Raw** tab → send e.g. `4A0100` (`InListPassiveTarget`, 1 target, 106 kbps Type A).
+2. Interpret response bytes per NXP **UM0701** / PN532 user manual.
+
+## 5. Continuous scan to WebSocket consumers
+
+1. Dashboard → **Start live scan**.
+2. Connect a WebSocket client to `ws://192.168.4.1/ws` (or `ws://pn532tool.local/ws`).
+3. Messages look like: `{"channel":"scan","payload":{...}}`