refactor(cli): decouple CLI commands from application services via command bus

Implemented a command bus architecture to decouple CLI command handling from application services. Added command_bus.py with Command, CommandHandler, and CommandBus classes, and command_registry.py to register handlers. Introduced BDD tests at features/cli_command_bus_decoupling.feature and corresponding step definitions in features/steps/cli_command_bus_steps.py to verify the decoupling behavior.

ISSUES CLOSED: #8880

features/cli_command_bus_decoupling.feature

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+Feature: CLI Command Bus Decoupling
+  As a developer
+  I want the CLI layer to be decoupled from application services
+  So that the architecture maintains proper separation of concerns
+
+  Background:
+    Given the command bus is initialized
+    And no handlers are registered
+
+  Scenario: Command bus can be created
+    When I create a new command bus
+    Then the command bus should be empty
+    And no handlers should be registered
+
+  Scenario: Handler registration
+    Given a command bus
+    When I register a handler for a command type
+    Then the handler should be registered
+    And the command bus should have the handler
+
+  Scenario: Command dispatch to registered handler
+    Given a command bus with a registered handler
+    When I dispatch a command
+    Then the handler should be invoked
+    And the result should be returned
+
+  Scenario: Dispatch fails for unregistered command
+    Given a command bus with no handlers
+    When I dispatch a command without a registered handler
+    Then a ValueError should be raised
+    And the error message should mention the command type
+
+  Scenario: Handler check
+    Given a command bus
+    When I check if a handler exists for a command type
+    Then the result should be accurate
+    And reflect the registration status
+
+  Scenario: Global command bus instance
+    When I get the global command bus
+    Then I should receive a CommandBus instance
+    And subsequent calls should return the same instance
+
+  Scenario: Set global command bus
+    Given a new command bus
+    When I set it as the global command bus
+    Then subsequent calls to get_command_bus should return it
+    And the previous instance should be replaced