feat: multi-issuer OIDC support with config consolidation

- Support multiple OAuth providers (core-api, tatlock-ui, tatlock)
- Changed oidc_issuer (string) to oidc_issuers (list)
- Per-issuer JWKS caching
- Validates token issuer against allowed list
- Consolidated config files (removed deprecated src/config.py, src/security.py)
- Updated imports to use src/shared/config and src/shared/security

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -160,8 +160,8 @@ docker run -p 8083:8083 core-code:latest
 | `HOMEASSISTANT_URL` | Home Assistant URL | `http://localhost:8123` |
 | `HOMEASSISTANT_TOKEN` | HA long-lived access token | - |
 | `OIDC_ENABLED` | Enable OIDC auth | `false` |
-| `OIDC_ISSUER` | OIDC issuer URL | - |
-| `OIDC_AUDIENCE` | OIDC audience | - |
+| `OIDC_ISSUERS` | OIDC issuer URLs (comma-separated) | See config.py |
+| `OIDC_AUDIENCES` | OIDC audiences (comma-separated) | See config.py |
 
 ## API Documentation