feat: PhantomKit v1.2.0 - auth, real probe sniffer, unicast deauth, webhooks, NTP, stealth mode and CI

Change 1 - GitHub Actions CI:
- .github/workflows/build.yml: compile firmware on every push/PR
- CI badge in README.md and README.es.md

Change 2 - NTP real timestamps:
- main.cpp: uplink WiFi AP+STA mode, NTP sync on boot
- config.h: UPLINK_SSID/PASSWORD, NTP_SERVER, NTP_OFFSET/DST defines
- credential_store.cpp: formatTimestamp() uses wall-clock time when NTP synced
- main.cpp: getTimestamp() shared helper with same NTP-aware logic

Change 3 - Stealth Mode:
- config.h: STEALTH_MODE define
- ap_manager.h/.cpp: setStealthMode() uses SDK softap_config.ssid_hidden
- web_server.cpp: POST /api/stealth endpoint, Ajustes tab with toggle button

Change 4 - Dashboard Auth:
- config.h: DASHBOARD_PASSWORD define
- web_server.h/.cpp: session token, /login GET/POST, /logout, isAuthenticated()
- All /dashboard and /api/* routes require valid session cookie
- Logout button in header

Change 5 - Real Probe Sniffer:
- probe_sniffer.cpp: IRAM_ATTR callback probePromiscCb() parses 802.11 frames
- Extracts Source MAC (buf[46..51]), SSID tag (buf[60+]), RSSI from RxControl
- wifi_promiscuous_enable(1) on start, disable on stop
- Dashboard shows device table: MAC, sought SSIDs, RSSI
- GET /api/probe/devices returns live device JSON

Change 6 - Deauth unicast:
- deauth.h/.cpp: clientMACs list, parseBSSID(), scanClients()
- scanClients() uses IRAM_ATTR callback to detect associated clients
- update() sends unicast AP->Client and Client->AP deauths + broadcast fallback
- 800ms passive scan window before each attack

Change 7 - Webhooks (notifier):
- notifier.h/.cpp: NotifierModule with HTTP POST to ntfy.sh or generic endpoint
- Config persisted in /notify.cfg on LittleFS
- credential_store.cpp: notifier.notify() called on every capture
- Dashboard Ajustes tab: URL/topic fields, Guardar and Probar buttons
- POST /api/notify with action=save or action=test

Author: chrisq-dev

.github/workflows/build.yml

@@ -0,0 +1,34 @@
+name: Build Firmware
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+
+      - name: Install PlatformIO
+        run: pip install platformio
+
+      - name: Cache PlatformIO packages
+        uses: actions/cache@v4
+        with:
+          path: ~/.platformio
+          key: ${{ runner.os }}-platformio-${{ hashFiles('platformio.ini') }}
+          restore-keys: |
+            ${{ runner.os }}-platformio-
+
+      - name: Compile firmware
+        run: pio run