feat(project-management) : migrate core Projects/Tasks domain into module (back)

Tranche 2 of LST-65. Mechanical, behaviour-preserving move of the core
business domain into src/Module/ProjectManagement/. API operations,
securities, uriTemplates and the 38 MCP tool names are all unchanged.

- 10 entities + 2 enums moved to Domain/{Entity,Enum}; intra-module
  relations stay concrete, cross-module relations go through contracts
  (Project.client -> ClientInterface, Task/TaskDocument users ->
  UserInterface).
- 9 repositories split into Domain/Repository interfaces + Doctrine impls,
  bound in services.yaml; consumers inject the interfaces. find() kept off
  the interfaces (ServiceEntityRepository ?object compat) -> findById().
- State (7), MCP tools (38), controller, CalDavService/RecurrenceCalculator,
  3 Doctrine listeners and SwitchWorkflowOutput moved under Infrastructure/.
- doctrine.yaml: ProjectManagement mapping + resolve_target_entities of the
  3 module contracts repointed to the module (ClientInterface stays legacy).
- ProjectManagementModule registered (id project-management, 4 RBAC perms,
  not re-wired); sidebar my-tasks/projects gated by the module.
- Legacy not-yet-modularised consumers (Mail/Gitea/BookStack, Serializer,
  fixtures, tests) swapped to the module FQCN — transitional coupling to be
  cleaned in 2.4/2.5/2.6.

159 tests green, mapping valid, no API route regression, cs-fixer clean.

config/modules.php

@@ -8,9 +8,11 @@ declare(strict_types=1);
  */
 
 use App\Module\Core\CoreModule;
+use App\Module\ProjectManagement\ProjectManagementModule;
 use App\Module\TimeTracking\TimeTrackingModule;
 
 return [
     CoreModule::class,
     TimeTrackingModule::class,
+    ProjectManagementModule::class,
 ];