feat: F024 global AI assistant — contextual decision intelligence drawer

Wires the existing "AI Assistent" button in the TopBar and adds a 420px
slide-in drawer with context-aware suggestions, message thread, loading
animation, and action cards requiring manual confirmation. Template-based
mock service returns German-language answers keyed by route + question
keywords — no real LLM calls, no invented facts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/assistant/AssistantLoadingState.tsx

@@ -0,0 +1,51 @@
+import { Box, Typography } from '@mui/material'
+
+export function AssistantLoadingState() {
+  return (
+    <Box sx={{ display: 'flex', gap: 1, px: 2, py: 1.5, alignItems: 'flex-start' }}>
+      <Box
+        sx={{
+          width: 28,
+          height: 28,
+          borderRadius: '50%',
+          bgcolor: '#4f46e5',
+          display: 'flex',
+          alignItems: 'center',
+          justifyContent: 'center',
+          flexShrink: 0,
+        }}
+      >
+        <Typography variant="caption" sx={{ color: 'white', fontWeight: 700, fontSize: '0.625rem' }}>AI</Typography>
+      </Box>
+      <Box
+        sx={{
+          bgcolor: '#f1f5f9',
+          borderRadius: '0 8px 8px 8px',
+          px: 1.5,
+          py: 1,
+          display: 'flex',
+          gap: 0.5,
+          alignItems: 'center',
+        }}
+      >
+        {[0, 1, 2].map(i => (
+          <Box
+            key={i}
+            sx={{
+              width: 6,
+              height: 6,
+              borderRadius: '50%',
+              bgcolor: '#94a3b8',
+              animation: 'bounce 1.2s ease-in-out infinite',
+              animationDelay: `${i * 0.2}s`,
+              '@keyframes bounce': {
+                '0%, 80%, 100%': { transform: 'scale(0.8)', opacity: 0.5 },
+                '40%': { transform: 'scale(1.2)', opacity: 1 },
+              },
+            }}
+          />
+        ))}
+      </Box>
+    </Box>
+  )
+}