docs: update test count and fix pki.md inaccuracies

- README: update test count from 283 to 337
- pki.md: fix environment variable names (PKI_CA_PASSWORD)
- pki.md: correct CLI usage examples (config via env/file)
- pki.md: update pki status output format
- pki.md: clarify revocation is API-only (no CLI command)

README.md

@@ -386,7 +386,7 @@ flaskpaste/
 │   └── api/
 │       ├── __init__.py  # Blueprint setup
 │       └── routes.py    # API endpoints
-├── tests/               # Test suite (283 tests)
+├── tests/               # Test suite (337 tests)
 ├── data/                # SQLite database
 ├── run.py               # Development server
 ├── wsgi.py              # Production WSGI entry