fix(marker): reject reserved global-prefix names only on create

The global-prefix reservation belongs on the create path, where it keeps
user-chosen names disjoint from inherited global-{name} markers. It was
implemented as a field_validator on MarkerCreate / MarkerDefinitionCreate,
which also back the PUT update bodies — so updating an inherited marker
while echoing its name in the body tripped the validator with a generic
422 before the controller could return the actionable 409 ("inherited,
use the marker-definitions API").

Drop the schema validators and enforce the prefix in the two create routes
(ControllerError -> 409). PUT no longer validates the body name (ignored
anyway — the target is the {name} path param), so editing an inherited
marker now reaches the controller's inheritance guard and returns the
clear 409. The name-format regex stays on the schema (still 422).

gns3server/api/routes/controller/links.py

@@ -458,6 +458,8 @@ async def create_marker(
     # uuid suffix avoids the collision that `marker-{link.id[:8]}` alone would
     # cause on the second anonymous marker on the same link (start_marker
     # rejects duplicate names).
+    if marker_data.name and marker_data.name.lower().startswith("global"):
+        raise ControllerError('Names starting with "global" are reserved for inherited markers')
     name = marker_data.name or f"marker-{link.id[:8]}-{uuid4().hex[:4]}"
     await link.start_marker(
         name=name,

gns3server/api/routes/controller/projects.py

@@ -260,6 +260,8 @@ async def create_marker_definition(
     Required privilege: Project.Modify
     """
 
+    if def_data.name and def_data.name.lower().startswith("global"):
+        raise ControllerError('Names starting with "global" are reserved for inherited markers')
     name = def_data.name or f"def-{project.id[:8]}"
     await project.create_marker_definition(
         name=name,

gns3server/schemas/controller/links.py

@@ -14,7 +14,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-from pydantic import BaseModel, Field, field_validator
+from pydantic import BaseModel, Field
 from typing import List, Optional, Tuple
 from enum import Enum
 from uuid import UUID, uuid4
@@ -176,13 +176,6 @@ class MarkerCreate(BaseModel):
         description="Whether the marker is active. Defaults to true on creation.",
     )
 
-    @field_validator("name")
-    @classmethod
-    def _check_name_not_reserved(cls, v):
-        if v is not None and v.lower().startswith("global"):
-            raise ValueError('Names starting with "global" are reserved')
-        return v
-
 
 class MarkerDefinitionCreate(BaseModel):
     """
@@ -215,11 +208,4 @@ class MarkerDefinitionCreate(BaseModel):
         ),
     )
 
-    @field_validator("name")
-    @classmethod
-    def _check_name_not_reserved(cls, v):
-        if v is not None and v.lower().startswith("global"):
-            raise ValueError('Names starting with "global" are reserved')
-        return v
-