feat: Improve DID registration with admin credentials

- Add admin keypair (DID + private key) for proper registration signing
- Remove SQLite database dependency for admin DID lookup
- Update both TypeScript and Python implementations to use admin credentials
- Enhance documentation with detailed usage, options, and security notes
- Fix JWT signing to use admin's key as issuer
- Standardize API URL handling with defaults
- Add command-line options for admin DID and API URL override

Both implementations now successfully register new DIDs using the admin's
credentials to sign the registration claims. The admin acts as both the
agent in the claim and the issuer of the JWT.

package.json

@@ -31,7 +31,7 @@
     "pywebview:package-win": "vite build --mode pywebview --config vite.config.pywebview.mts && .venv/Scripts/python -m PyInstaller --name TimeSafari --add-data 'dist;www' src/pywebview/main.py",
     "pywebview:package-mac": "vite build --mode pywebview --config vite.config.pywebview.mts && .venv/bin/python -m PyInstaller --name TimeSafari --add-data 'dist:www' src/pywebview/main.py",
     "build:did-generator": "tsc -p test-scripts/tsconfig.json",
-    "generate-did": "node test-scripts/dist/did_generator.js --db-path ../endorser-ch-test-local.sqlite3"
+    "generate-did": "node test-scripts/dist/did_generator.js"
   },
   "dependencies": {
     "@capacitor/android": "^6.2.0",