feat: migrate all icons to Lucide React

Replace unicode characters, emoji, and inline SVGs with lucide-react
components across the entire design system and page layer. Update
tests to assert on SVG elements instead of text content.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/pages/RouteDetail/RouteDetail.tsx

@@ -1,5 +1,6 @@
 import { useMemo } from 'react'
 import { useParams, useNavigate } from 'react-router-dom'
+import { AlertTriangle } from 'lucide-react'
 import styles from './RouteDetail.module.css'
 
 // Layout
@@ -337,7 +338,7 @@ export function RouteDetail() {
             expandedContent={(row) =>
               row.errorMessage ? (
                 <div className={styles.inlineError}>
-                  <span className={styles.inlineErrorIcon}>⚠</span>
+                  <span className={styles.inlineErrorIcon}><AlertTriangle size={14} /></span>
                   <div>
                     <div className={styles.errorClass}>{row.errorClass}</div>
                     <div className={styles.errorText}>{row.errorMessage}</div>