Add region manager assignment endpoints

Distribution/Features/Region/RegionController.cs

@@ -43,6 +43,34 @@ public class RegionController(RegionService service) : ControllerBase
         return deleted ? NoContent() : NotFound();
     }
 
+    [HttpGet("{id:guid}/manager")]
+    public async Task<IActionResult> GetManager(Guid id)
+    {
+        var result = await service.GetManagerAsync(id);
+        return result is null ? NotFound() : Ok(result);
+    }
+
+    [HttpPut("{id:guid}/manager")]
+    public async Task<IActionResult> SetManager(Guid id, SetRegionManagerRequest request, CancellationToken ct)
+    {
+        try
+        {
+            var result = await service.SetManagerAsync(id, request, ct);
+            return result is null ? NotFound() : Ok(result);
+        }
+        catch (InvalidOperationException ex)
+        {
+            return BadRequest(new { error = ex.Message });
+        }
+    }
+
+    [HttpDelete("{id:guid}/manager")]
+    public async Task<IActionResult> RemoveManager(Guid id, CancellationToken ct)
+    {
+        var removed = await service.RemoveManagerAsync(id, ct);
+        return removed ? NoContent() : NotFound();
+    }
+
     //targets/budgets/agencies/tax-rule.
     [HttpPut("{id:guid}/manage")]
     public async Task<IActionResult> Manage(Guid id, ManageRegionRequest request, CancellationToken ct)