marker: rework pause/resume from project-wide to per-definition

The project-wide mute (POST /markers/pause|resume + _markers_paused) paused
every marker with one button. The actual need is per-rule control: pause one
definition and toggle only its inherited global-{name} copies across all links.

- Drop project-level: _markers_paused (init/asdict/load/start_all), the
  pause_all/resume_all_markers methods, and the /markers/pause|resume routes.
- Add per-definition: a persisted `paused` flag on each definition;
  pause/resume_marker_definition fan out update_marker(enabled) to every
  global-{name} copy — instant, via the existing enable_packet_filter toggle
  (no NIO rebuild, pcap/emitted preserved). New links inherit a paused
  definition already off (inherit_marker passes enabled=not paused).
- start_marker takes an enabled kwarg; update_marker's enabled-only short-circuit
  now also covers inherited copies so def pause/resume is instant.
- Routes: POST /marker-definitions/{name}/pause|resume.
- Docs + tests updated.

gns3server/controller/udp_link.py

@@ -350,7 +350,7 @@ class UDPLink(Link):
         # explicitly deletes a marker via the REST API, and a marker is torn
         # down automatically only when its link is deleted.
 
-    async def start_marker(self, name, bpf, tag=None, direction=None, capture_node_id=None, color=None, highlight_duration=None, inherited_from=None):
+    async def start_marker(self, name, bpf, tag=None, direction=None, capture_node_id=None, color=None, highlight_duration=None, enabled=True, inherited_from=None):
         """
         Attach a traffic-insight marker to this link.
 
@@ -390,7 +390,7 @@ class UDPLink(Link):
         marker_entry = {
             "bpf": bpf,
             "tag": tag,
-            "enabled": True,
+            "enabled": enabled,
             "color": color,
             "highlight_duration": highlight_duration,
             "capture_node_id": marker_side["node"].id,
@@ -472,7 +472,7 @@ class UDPLink(Link):
             and color is None
             and highlight_duration is None
         )
-        if only_enabled and self._created and not marker_info.get("inherited_from"):
+        if only_enabled and self._created:
             capture_node_id = marker_info.get("capture_node_id")
             side = next((s for s in self._nodes if str(s["node"].id) == str(capture_node_id)), None)
             if side is not None: