license: switch from BSL-1.1 to MIT

MIT is true open source (OSI-approved) and provides the same liability
protection through its warranty disclaimer. The strengthened disclaimer
covering silent third-party failures, regulatory non-compliance, and
user verification responsibility is retained in the LICENSE file.

BSL restricted commercial use but didn't add legal protection — the
liability limitation is what protects against lawsuits, and that works
the same under MIT.

https://claude.ai/code/session_01KF4i7Ra7zCEDskxDBaNtcT

package.json

@@ -2,7 +2,7 @@
   "name": "silent-send",
   "version": "0.9.3",
   "private": true,
-  "license": "BSL-1.1",
+  "license": "MIT",
   "description": "Browser extension that substitutes personal data before sending to AI services",
   "scripts": {
     "build:chrome": "./build.sh chrome",