feat: add logo, favicon, and theme system

- Add custom SVG favicon and Logo component (house + network nodes motif)
- Update page title to Homelable with meta description
- Show Logo in sidebar header and toolbar
- Add theme store and ThemeModal for canvas style switching
- Refactor node colors and edge styles for theme support

frontend/src/components/canvas/edges/index.tsx

@@ -7,6 +7,8 @@ import {
   type Edge,
 } from '@xyflow/react'
 import type { EdgeData, EdgeType } from '@/types'
+import { useThemeStore } from '@/stores/themeStore'
+import { THEMES } from '@/utils/themes'
 
 const VLAN_COLORS = ['#00d4ff', '#a855f7', '#39d353', '#ff6e00', '#e3b341', '#f85149']
 
@@ -15,28 +17,33 @@ function getVlanColor(vlanId?: number): string {
   return VLAN_COLORS[vlanId % VLAN_COLORS.length]
 }
 
-const EDGE_STYLES: Record<EdgeType, React.CSSProperties> = {
-  ethernet: { stroke: '#30363d', strokeWidth: 2 },
-  wifi: { stroke: '#00d4ff', strokeWidth: 1.5, strokeDasharray: '6 3' },
-  iot: { stroke: '#e3b341', strokeWidth: 1.5, strokeDasharray: '2 4' },
-  vlan: { strokeWidth: 2.5 },
-  virtual: { stroke: '#8b949e', strokeWidth: 1, strokeDasharray: '4 4' },
-  cluster: { stroke: '#ff6e00', strokeWidth: 2.5, strokeDasharray: '8 3' },
-}
-
 export function HomelableEdge({ id, sourceX, sourceY, targetX, targetY, sourcePosition, targetPosition, data, selected }: EdgeProps<Edge<EdgeData>>) {
+  const activeTheme = useThemeStore((s) => s.activeTheme)
+  const theme = THEMES[activeTheme]
+
   const pathArgs = { sourceX, sourceY, sourcePosition, targetX, targetY, targetPosition }
   const [edgePath, labelX, labelY] = data?.path_style === 'smooth'
     ? getSmoothStepPath({ ...pathArgs, borderRadius: 8 })
     : getBezierPath(pathArgs)
 
   const edgeType: EdgeType = data?.type ?? 'ethernet'
+  const edgeColors = theme.colors.edgeColors
+
+  const BASE_STYLES: Record<EdgeType, React.CSSProperties> = {
+    ethernet: { stroke: edgeColors.ethernet, strokeWidth: 2 },
+    wifi:     { stroke: edgeColors.wifi,     strokeWidth: 1.5, strokeDasharray: '6 3' },
+    iot:      { stroke: edgeColors.iot,      strokeWidth: 1.5, strokeDasharray: '2 4' },
+    vlan:     { strokeWidth: 2.5 },
+    virtual:  { stroke: edgeColors.virtual,  strokeWidth: 1,   strokeDasharray: '4 4' },
+    cluster:  { stroke: edgeColors.cluster,  strokeWidth: 2.5, strokeDasharray: '8 3' },
+  }
+
   const customColor = data?.custom_color as string | undefined
   const style: React.CSSProperties = {
-    ...EDGE_STYLES[edgeType],
+    ...BASE_STYLES[edgeType],
     ...(edgeType === 'vlan' ? { stroke: getVlanColor(data?.vlan_id as number | undefined) } : {}),
     ...(customColor ? { stroke: customColor } : {}),
-    ...(selected ? { stroke: '#00d4ff', filter: 'drop-shadow(0 0 4px #00d4ff88)' } : {}),
+    ...(selected ? { stroke: theme.colors.edgeSelectedColor, filter: `drop-shadow(0 0 4px ${theme.colors.edgeSelectedColor}88)` } : {}),
   }
 
   return (
@@ -48,9 +55,9 @@ export function HomelableEdge({ id, sourceX, sourceY, targetX, targetY, sourcePo
             className="absolute pointer-events-none font-mono text-[10px] px-1 rounded"
             style={{
               transform: `translate(-50%, -50%) translate(${labelX}px, ${labelY}px)`,
-              background: '#161b22',
-              color: '#8b949e',
-              border: '1px solid #30363d',
+              background: theme.colors.edgeLabelBackground,
+              color:      theme.colors.edgeLabelColor,
+              border:     `1px solid ${theme.colors.edgeLabelBorder}`,
             }}
           >
             {data.label as string}