Add API tokens and OAuth2 client support for external integrations

- Personal API tokens (model, user-settings UI, admin, management command,
  DRF auth class) for non-interactive API access from automations like n8n.
  Raw token shown once; only a SHA-256 hash is stored; last_used_at writes
  are throttled.
- OAuth2 authorization server via django-oauth-toolkit with authorization
  server metadata and optional, off-by-default Dynamic Client Registration
  (RFC 7591), so remote OAuth/MCP clients can authenticate and self-register.
- Tests for token auth, DCR gating and the management commands, plus
  .env.example and README documentation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/apps/users/urls.py

@@ -32,6 +32,16 @@ urlpatterns = [
         views.update_settings,
         name="user_settings",
     ),
+    path(
+        "user/api-tokens/add/",
+        views.api_token_add,
+        name="user_api_token_add",
+    ),
+    path(
+        "user/api-tokens/<int:token_id>/revoke/",
+        views.api_token_revoke,
+        name="user_api_token_revoke",
+    ),
     path(
         "users/",
         views.users_index,