feat: brain-engine + brain-ui + docs — template full stack standalone

- brain-engine: server, embed, search, RAG, MCP, start.sh (standalone)
- brain-ui: source React complète, build.sh, DocsView avec tier colors
- docs: 14 pages guides humains (getting-started, architecture, sessions, workflows, agents, vues tier)
- brain-compose.yml v0.9.0: tier featured ajouté, sessions/agents par tier, coach_level, API key schema
- DISTRIBUTION_CHECKLIST v1.2: brain-engine + brain-ui + docs dans la checklist

brain-ui/tailwind.config.js

@@ -0,0 +1,20 @@
+export default {
+  content: ['./index.html', './src/**/*.{ts,tsx}'],
+  theme: {
+    extend: {
+      colors: {
+        brain: {
+          bg:      '#0d0d0d',
+          surface: '#1a1a1a',
+          border:  '#2a2a2a',
+          accent:  '#6366f1',
+          gate:    '#f59e0b',
+          ok:      '#22c55e',
+          fail:    '#ef4444',
+          muted:   '#6b7280',
+        }
+      }
+    }
+  },
+  plugins: []
+}