Add USB, Notifications, Network plugins and reusable EmployeeSearch component

New Plugins:
- USB plugin: Device checkout/checkin with employee lookup, checkout history
- Notifications plugin: Announcements with types, scheduling, shopfloor display
- Network plugin: Network device management with subnets and VLANs
- Equipment and Computers plugins: Asset type separation

Frontend:
- EmployeeSearch component: Reusable employee lookup with autocomplete
- USB views: List, detail, checkout/checkin modals
- Notifications views: List, form with recognition mode
- Network views: Device list, detail, form
- Calendar view with FullCalendar integration
- Shopfloor and TV dashboard views
- Reports index page
- Map editor for asset positioning
- Light/dark mode fixes for map tooltips

Backend:
- Employee search API with external lookup service
- Collector API for PowerShell data collection
- Reports API endpoints
- Slides API for TV dashboard
- Fixed AppVersion model (removed BaseModel inheritance)
- Added checkout_name column to usbcheckouts table

Styling:
- Unified detail page styles
- Improved pagination (page numbers instead of prev/next)
- Dark/light mode theme improvements

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

shopdb/core/models/relationship.py

@@ -1,11 +1,11 @@
-"""Machine relationship models."""
+"""Machine and Asset relationship models."""
 
 from shopdb.extensions import db
 from .base import BaseModel
 
 
 class RelationshipType(BaseModel):
-    """Types of relationships between machines."""
+    """Types of relationships between machines/assets."""
     __tablename__ = 'relationshiptypes'
 
     relationshiptypeid = db.Column(db.Integer, primary_key=True)
@@ -21,6 +21,65 @@ class RelationshipType(BaseModel):
         return f"<RelationshipType {self.relationshiptype}>"
 
 
+class AssetRelationship(BaseModel):
+    """
+    Relationships between assets.
+
+    Examples:
+    - Computer controls Equipment
+    - Two machines are dualpath partners
+    - Network device connects to equipment
+    """
+    __tablename__ = 'assetrelationships'
+
+    relationshipid = db.Column(db.Integer, primary_key=True)
+
+    source_assetid = db.Column(
+        db.Integer,
+        db.ForeignKey('assets.assetid'),
+        nullable=False
+    )
+    target_assetid = db.Column(
+        db.Integer,
+        db.ForeignKey('assets.assetid'),
+        nullable=False
+    )
+    relationshiptypeid = db.Column(
+        db.Integer,
+        db.ForeignKey('relationshiptypes.relationshiptypeid'),
+        nullable=False
+    )
+
+    notes = db.Column(db.Text)
+
+    # Relationships
+    source_asset = db.relationship(
+        'Asset',
+        foreign_keys=[source_assetid],
+        backref='outgoing_relationships'
+    )
+    target_asset = db.relationship(
+        'Asset',
+        foreign_keys=[target_assetid],
+        backref='incoming_relationships'
+    )
+    relationship_type = db.relationship('RelationshipType', backref='asset_relationships')
+
+    __table_args__ = (
+        db.UniqueConstraint(
+            'source_assetid',
+            'target_assetid',
+            'relationshiptypeid',
+            name='uq_asset_relationship'
+        ),
+        db.Index('idx_asset_rel_source', 'source_assetid'),
+        db.Index('idx_asset_rel_target', 'target_assetid'),
+    )
+
+    def __repr__(self):
+        return f"<AssetRelationship {self.source_assetid} -> {self.target_assetid}>"
+
+
 class MachineRelationship(BaseModel):
     """
     Relationships between machines.