Add netbox_rack_concept plugin: rack blueprint planning

Introduces a NetBox 4.6 plugin for planning rack layouts (RackConcept,
ConceptDevice) without creating real dcim.Rack/dcim.Device objects, so
blueprints never appear in rack/device lists, utilization reports, or
IPAM.

Features:
- Copy paths: real rack -> concept, concept -> concept (clone), and
  concept -> one or more real racks (deploy, with name patterning and
  dry-run support)
- Manual concept creation via a dedicated "Rack Concepts" nav menu
- Tenant and tenant group assignment on concepts and planned devices
- Partial-width device placement (1/1-1/4) with slot-based collision
  detection, matching netbox_utilities' partial-width feature
- Custom drag-and-drop elevation (netbox-reorder-rack operates on real
  Device querysets, which concepts don't have) with server-side
  validation of every move
- Full REST API, filtering, CSV import, bulk edit, search integration
- Optional, config-driven interop with netbox_utilities (partial-width
  field mapping) and netbox-reorder-rack, degrading gracefully when
  either plugin is absent

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

netbox_rack_concept/search.py

@@ -0,0 +1,27 @@
+from netbox.search import SearchIndex, register_search
+
+from .models import ConceptDevice, RackConcept
+
+
+@register_search
+class RackConceptIndex(SearchIndex):
+    model = RackConcept
+    fields = (
+        ('name', 100),
+        ('description', 500),
+        ('comments', 5000),
+    )
+    display_attrs = ('status', 'tenant', 'description')
+
+
+@register_search
+class ConceptDeviceIndex(SearchIndex):
+    model = ConceptDevice
+    fields = (
+        ('name', 100),
+        ('label', 110),
+        ('serial', 120),
+        ('description', 500),
+        ('comments', 5000),
+    )
+    display_attrs = ('concept', 'status', 'device_type', 'role', 'description')