feat: rename keep-notes to memento-note, migrate to PostgreSQL, fix MCP bugs

- Rename directory keep-notes -> memento-note with all code references
- Prisma: SQLite -> PostgreSQL (both app and MCP server schemas)
- Sync MCP schema with main app (add missing fields, relations, indexes)
- Delete 17 SQLite migrations (clean slate for PostgreSQL)
- Remove SQLite dependencies (@libsql/client, better-sqlite3, etc.)
- Fix MCP server: hardcoded Windows DB paths -> DATABASE_URL env var
- Fix MCP server: .dockerignore excluded index-sse.js (SSE mode broken)
- MCP Dockerfile: node:20 -> node:22
- Docker Compose: add postgres service, remove SQLite volume
- Generate favicon.ico, icon-192.png, icon-512.png, apple-icon.png
- Update layout.tsx icons and manifest.json for PNG icons
- Update all .env files for PostgreSQL
- Rewrite README.md with updated sections
- Remove mcp-server/node_modules and prisma/client-generated from git tracking

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

memento-note/components/demo-mode-toggle.tsx

@@ -0,0 +1,101 @@
+'use client'
+
+import { useState } from 'react'
+import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
+import { Switch } from '@/components/ui/switch'
+import { FlaskConical, Zap, Target, Lightbulb } from 'lucide-react'
+import { toast } from 'sonner'
+import { useLanguage } from '@/lib/i18n'
+
+interface DemoModeToggleProps {
+  demoMode: boolean
+  onToggle: (enabled: boolean) => Promise<void>
+}
+
+export function DemoModeToggle({ demoMode, onToggle }: DemoModeToggleProps) {
+  const [isPending, setIsPending] = useState(false)
+  const { t } = useLanguage()
+
+  const handleToggle = async (checked: boolean) => {
+    setIsPending(true)
+    try {
+      await onToggle(checked)
+      if (checked) {
+        toast.success(t('demoMode.activated'))
+      } else {
+        toast.success(t('demoMode.deactivated'))
+      }
+    } catch (error) {
+      console.error('Error toggling demo mode:', error)
+      toast.error(t('demoMode.toggleFailed'))
+    } finally {
+      setIsPending(false)
+    }
+  }
+
+  return (
+    <Card className={`border-2 transition-all ${
+      demoMode
+        ? 'border-amber-300 bg-gradient-to-br from-amber-50 to-white dark:from-amber-950/30 dark:to-background'
+        : 'border-amber-100 dark:border-amber-900/30'
+    }`}>
+      <CardHeader className="pb-3">
+        <div className="flex items-center justify-between">
+          <div className="flex items-center gap-2">
+            <div className={`p-2 rounded-full transition-colors ${
+              demoMode
+                ? 'bg-amber-200 dark:bg-amber-900/50'
+                : 'bg-gray-100 dark:bg-gray-800'
+            }`}>
+              <FlaskConical className={`h-5 w-5 ${
+                demoMode ? 'text-amber-600 dark:text-amber-400' : 'text-gray-500'
+              }`} />
+            </div>
+            <div>
+              <CardTitle className="text-base flex items-center gap-2">
+                🧪 {t('demoMode.title')}
+                {demoMode && <Zap className="h-4 w-4 text-amber-500 animate-pulse" />}
+              </CardTitle>
+              <CardDescription className="text-xs mt-1">
+                {t('demoMode.description')}
+              </CardDescription>
+            </div>
+          </div>
+          <Switch
+            checked={demoMode}
+            onCheckedChange={handleToggle}
+            disabled={isPending}
+            className="data-[state=checked]:bg-amber-600"
+          />
+        </div>
+      </CardHeader>
+
+      {demoMode && (
+        <CardContent className="pt-0 space-y-2">
+          <div className="rounded-lg bg-white dark:bg-zinc-900 border border-amber-200 dark:border-amber-900/30 p-3">
+            <p className="text-xs font-semibold text-gray-700 dark:text-gray-300 mb-2">
+              {t('demoMode.parametersActive')}
+            </p>
+            <div className="space-y-1.5 text-xs text-gray-600 dark:text-gray-400">
+              <div className="flex items-start gap-2">
+                <Target className="h-3.5 w-3.5 mt-0.5 text-amber-600 flex-shrink-0" />
+                <span>{t('demoMode.similarityThreshold')}</span>
+              </div>
+              <div className="flex items-start gap-2">
+                <Zap className="h-3.5 w-3.5 mt-0.5 text-amber-600 flex-shrink-0" />
+                <span>{t('demoMode.delayBetweenNotes')}</span>
+              </div>
+              <div className="flex items-start gap-2">
+                <Lightbulb className="h-3.5 w-3.5 mt-0.5 text-amber-600 flex-shrink-0" />
+                <span>{t('demoMode.unlimitedInsights')}</span>
+              </div>
+            </div>
+          </div>
+          <p className="text-xs text-amber-700 dark:text-amber-400 text-center">
+            💡 {t('demoMode.createNotesTip')}
+          </p>
+        </CardContent>
+      )}
+    </Card>
+  )
+}