perf(web/icons): per-icon lucide imports via centralised alias

Route all lucide-react icon usage through a single src/icons.ts
re-export that imports each icon from its own per-icon module
(lucide-react/dist/esm/icons/<name>) instead of the barrel.

Bundle-size impact: none (29kB icons chunk unchanged — tree-shaking
was already effective with sideEffects:false). Dev-experience win:
Vite transforms 247 modules instead of 1848 because the dep
optimiser no longer pre-bundles the full lucide barrel — faster
cold start and HMR.

Ambient d.ts declares the wildcard module so TS accepts per-icon
imports; lucide ships .d.ts only for the barrel.

Seven icons were renamed upstream and still work through the barrel
via aliases (AlertTriangle -> triangle-alert, BarChart3 -> chart-column,
CheckCircle -> circle-check-big, Filter -> funnel, PlusCircle ->
circle-plus, Sliders -> sliders-vertical, UploadCloud -> cloud-upload,
Fingerprint -> fingerprint-pattern). Component call sites stay on
the legacy names; the renames live only in icons.ts.

decnet_web/src/components/Dashboard.tsx

@@ -1,7 +1,7 @@
 import React, { useEffect, useMemo, useRef, useState } from 'react';
 import { useNavigate } from 'react-router-dom';
 import './Dashboard.css';
-import { Shield, Users, Activity, Clock, Paperclip, Crosshair, Flame, Archive, ShieldOff, Server } from 'lucide-react';
+import { Shield, Users, Activity, Clock, Paperclip, Crosshair, Flame, Archive, ShieldOff, Server } from '../icons';
 import { parseEventBody } from '../utils/parseEventBody';
 import ArtifactDrawer from './ArtifactDrawer';
 import EmptyState from './EmptyState/EmptyState';