fix: add missing 'test' script to package.json

## Problem
npm test was failing with 'Missing script: test' error.
Project has Python tests but package.json only defined test:decoder script.

## Solution
Added test scripts to package.json:
- test: Runs pytest (default npm test command)
- test:python: Explicit Python test runner
- test:coverage: Runs tests with coverage report

## Verification
✓ npm test now runs successfully
✓ All 56 Python tests pass
✓ 2.54s execution time

Test suite includes:
- 4 RTL_433 integration tests
- 26 GPS validation tests
- 15 preamble/frequency tests
- 11 timing analyzer tests

🎯 Generated with [Claude Code](https://claude.com/claude-code)

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

package.json

@@ -4,7 +4,10 @@
   "description": "IoT RF Device Mapping Platform - Wigle for Sub-GHz Signals",
   "type": "module",
   "scripts": {
-    "test:decoder": "node static/js/decoder/test.js"
+    "test": "python -m pytest tests/ -v",
+    "test:decoder": "node static/js/decoder/test.js",
+    "test:python": "python -m pytest tests/ -v",
+    "test:coverage": "python -m pytest tests/ --cov=src --cov-report=html"
   },
   "keywords": [
     "rf",