feat: rewrite busylight as FastAPI web application with SQLite

Replace the standalone Python script + config.cfg with a full web
application featuring:
- FastAPI backend with REST API
- SQLite database (config, state, activity log separated)
- Bootstrap 5 web interface for configuration
- Pages: Dashboard, Users, Devices, Assignments, Color Rules, Settings, Log
- APScheduler background polling for Teams presence + AIDA status
- systemd service file for Linux deployment
- Migration script to import existing config.cfg data

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

wled_client.py

@@ -0,0 +1,26 @@
+import logging
+import requests
+
+logger = logging.getLogger(__name__)
+
+TIMEOUT = 5
+
+
+def build_wled_url(hostname, r, g, b, segment=None, effect=""):
+    """Build WLED HTTP API URL."""
+    base = f"http://{hostname}/win&A=255&R={r}&G={g}&B={b}"
+    if effect:
+        base = f"http://{hostname}{effect}&R={r}&G={g}&B={b}"
+    if segment is not None:
+        base = f"{base}&SS={segment}"
+    return base
+
+
+def call_wled(url):
+    """Send HTTP request to WLED device. Returns (success, status_text)."""
+    try:
+        r = requests.post(url, timeout=TIMEOUT)
+        return True, f"{r.status_code} {r.reason}"
+    except requests.exceptions.RequestException as e:
+        logger.warning("WLED nicht erreichbar: %s - %s", url, e)
+        return False, str(e)