🔒️(backend) secure native app OIDC login with exchange codes

Add one-time exchange code mechanism for native app OIDC login.
Instead of exposing session ID in redirect URL, generates a
short-lived single-use code stored in Redis. Native apps exchange
this code for the session ID via a dedicated API endpoint.

Includes NativeAppRedirect for custom URL schemes, rate limiting,
logging, and whitelist of allowed schemes.

Closes #1153

Co-Authored-By: gigi206

Makefile

@@ -191,7 +191,6 @@ lint-pylint: ## lint back-end python sources with pylint only on changed files f
 
 test: ## run project tests
 	@$(MAKE) test-back-parallel
-	@$(MAKE) test-summary
 .PHONY: test
 
 test-back: ## run back-end tests
@@ -204,11 +203,6 @@ test-back-parallel: ## run all back-end tests in parallel
 	bin/pytest -n auto $${args:-${1}}
 .PHONY: test-back-parallel
 
-test-summary: ## run summary tests
-	@args="$(filter-out $@,$(MAKECMDGOALS))" && \
-	bin/pytest-summary $${args:-${1}}
-.PHONY: test-summary
-
 makemigrations:  ## run django makemigrations for the Meet project.
 	@echo "$(BOLD)Running makemigrations$(RESET)"
 	@$(COMPOSE) up -d postgresql