Fix tshark hex parsing and add API key settings UI

Parse tshark GSM field values with int(value, 0) instead of int(value)
to auto-detect hex 0x-prefixed output (e.g. 0x039e for TMSI/LAC/CID).
Without this, every tshark line with hex values fails to parse, causing
0 devices to be captured during monitoring.

Also add API Keys tab to Settings modal for configuring OpenCellID key
via the UI (in addition to env var), with status display and usage bar.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

utils/gsm_geocoding.py

@@ -65,6 +65,15 @@ def lookup_cell_coordinates(mcc: int, mnc: int, lac: int, cid: int) -> dict[str,
         return None
 
 
+def _get_api_key() -> str:
+    """Get OpenCellID API key at runtime (env var first, then database)."""
+    env_key = config.GSM_OPENCELLID_API_KEY
+    if env_key:
+        return env_key
+    from utils.database import get_setting
+    return get_setting('gsm.opencellid.api_key', '')
+
+
 def lookup_cell_from_api(mcc: int, mnc: int, lac: int, cid: int) -> dict[str, Any] | None:
     """
     Lookup cell tower from OpenCellID API and cache result.
@@ -81,9 +90,14 @@ def lookup_cell_from_api(mcc: int, mnc: int, lac: int, cid: int) -> dict[str, An
         Returns None if API call fails or cell not found.
     """
     try:
+        api_key = _get_api_key()
+        if not api_key:
+            logger.warning("OpenCellID API key not configured")
+            return None
+
         api_url = config.GSM_OPENCELLID_API_URL
         params = {
-            'key': config.GSM_OPENCELLID_API_KEY,
+            'key': api_key,
             'mcc': mcc,
             'mnc': mnc,
             'lac': lac,