feat: replace static hardware fields with dynamic node properties

Replaces the 4 fixed hardware columns (cpu_count, cpu_model, ram_gb,
disk_gb) with a flexible properties system. Each property has a key,
value, icon (from a curated Lucide picker), and a visibility toggle
that controls whether it appears on the canvas node card.

- Backend: add `properties` JSON column to Node model; data migration
  converts existing hardware rows to properties with correct icons
  (idempotent, old columns kept for safety)
- Backend: add `properties` to NodeBase, NodeUpdate, NodeSave schemas
  and canvasSerializer so values survive canvas save/load
- Frontend: add NodeProperty type; new propertyIcons.ts registry (20
  icons); BaseNode renders visible properties with legacy hardware
  fallback for unmigrated nodes
- Frontend: DetailPanel gains interactive properties section (add /
  edit / remove / toggle visibility / icon picker) replacing the
  read-only hardware block; hardware section removed from NodeModal
- Tests: 6 migration tests, 7 API tests, 8 DetailPanel property tests,
  6 BaseNode render/fallback tests, 9 propertyIcons util tests

frontend/src/components/canvas/nodes/BaseNode.tsx

@@ -4,6 +4,7 @@ import { Cpu, MemoryStick, HardDrive, type LucideIcon } from 'lucide-react'
 import type { NodeData } from '@/types'
 import { resolveNodeColors } from '@/utils/nodeColors'
 import { resolveNodeIcon } from '@/utils/nodeIcons'
+import { resolvePropertyIcon } from '@/utils/propertyIcons'
 import { useThemeStore } from '@/stores/themeStore'
 import { THEMES } from '@/utils/themes'
 import { useCanvasStore } from '@/stores/canvasStore'
@@ -31,7 +32,11 @@ export function BaseNode({ id, data, selected, icon: typeIcon, width, height }:
   const colors = resolveNodeColors(data, activeTheme)
   const statusColor = theme.colors.statusColors[data.status]
   const isOnline = data.status === 'online'
-  const showHardware = data.show_hardware && (data.cpu_count != null || data.cpu_model || data.ram_gb != null || data.disk_gb != null)
+
+  // Properties: prefer new system; fall back to legacy hardware fields for unmigrated nodes
+  const visibleProperties = data.properties?.filter((p) => p.visible) ?? null
+  const showLegacyHardware = !data.properties && data.show_hardware &&
+    (data.cpu_count != null || data.cpu_model || data.ram_gb != null || data.disk_gb != null)
 
   return (
     <div
@@ -102,12 +107,30 @@ export function BaseNode({ id, data, selected, icon: typeIcon, width, height }:
         </div>
       </div>
 
-      {/* Hardware section */}
-      {showHardware && (
+      {/* Properties section (new system) */}
+      {visibleProperties && visibleProperties.length > 0 && (
+        <>
+          <div style={{ height: 1, background: `${colors.border}44`, margin: '0 8px' }} />
+          <div className="flex flex-col gap-1 px-2.5 py-1.5">
+            {visibleProperties.map((prop, i) => {
+              const Icon = resolvePropertyIcon(prop.icon)
+              return (
+                <div key={i} className="flex items-center gap-1 font-mono text-[10px]" style={{ color: theme.colors.nodeSubtextColor }}>
+                  {Icon && <Icon size={9} className="shrink-0" />}
+                  <span className="truncate max-w-[60px] shrink-0" title={prop.key}>{prop.key}</span>
+                  <span className="truncate" title={prop.value}>· {prop.value}</span>
+                </div>
+              )
+            })}
+          </div>
+        </>
+      )}
+
+      {/* Legacy hardware section — fallback for nodes not yet migrated */}
+      {showLegacyHardware && (
         <>
           <div style={{ height: 1, background: `${colors.border}44`, margin: '0 8px' }} />
           <div className="flex flex-col gap-1 px-2.5 py-1.5">
-            {/* Line 1: CPU */}
             {(data.cpu_model || data.cpu_count != null) && (
               <div className="flex items-center gap-1 font-mono text-[10px]" style={{ color: theme.colors.nodeSubtextColor }}>
                 <Cpu size={9} className="shrink-0" />
@@ -119,7 +142,6 @@ export function BaseNode({ id, data, selected, icon: typeIcon, width, height }:
                 )}
               </div>
             )}
-            {/* Line 2: RAM + Disk */}
             {(data.ram_gb != null || data.disk_gb != null) && (
               <div className="flex items-center gap-2 font-mono text-[10px]" style={{ color: theme.colors.nodeSubtextColor }}>
                 {data.ram_gb != null && (