docs: Add dynamic routing integration architecture documentation.

Add a new Documentation/topics/dynamic-routing/ section covering:
- OVN's integration model with external routing daemons
- Architecture diagrams for IP route exchange and EVPN
- Deployment scenario diagrams for both IP routing and EVPN
- IP route advertisement and learning mechanisms
- VRF management
- EVPN remote VTEP discovery, FDB/neighbor learning, and
  Advertised MAC Binding

Reported-at: https://redhat.atlassian.net/browse/FDP-3118
Assisted-by: Claude, with model: claude-opus-4-6
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Ales Musil <amusil@redhat.com>

Author: dceara

Documentation/automake.mk

@@ -27,6 +27,8 @@ DOC_SOURCE = \
 	Documentation/topics/testing.rst \
 	Documentation/topics/test-development.rst \
 	Documentation/topics/high-availability.rst \
+	Documentation/topics/dynamic-routing/architecture.rst \
+	Documentation/topics/dynamic-routing/index.rst \
 	Documentation/topics/incremental-processing/datapath-sync-graph.png \
 	Documentation/topics/incremental-processing/evpn-arp-graph.png \
 	Documentation/topics/incremental-processing/ic-graph.png \