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/lib/i18n/detect-user-language.ts

@@ -0,0 +1,62 @@
+/**
+ * Detect user's preferred language from their existing notes
+ * Analyzes language distribution across all user's notes
+ */
+
+import { auth } from '@/auth'
+import { prisma } from '@/lib/prisma'
+import { SupportedLanguage } from './load-translations'
+
+export async function detectUserLanguage(): Promise<SupportedLanguage> {
+  const session = await auth()
+
+  // Default to English for non-logged-in users
+  if (!session?.user?.id) {
+    return 'en'
+  }
+
+  try {
+    // Get all user's notes with detected languages
+    const notes = await prisma.note.findMany({
+      where: {
+        userId: session.user.id,
+        language: { not: null }
+      },
+      select: {
+        language: true,
+        languageConfidence: true
+      }
+    })
+
+    if (notes.length === 0) {
+      return 'en' // Default for new users
+    }
+
+    // Count language occurrences weighted by confidence
+    const languageScores: Record<string, number> = {}
+
+    for (const note of notes) {
+      if (note.language) {
+        const confidence = note.languageConfidence || 0.8
+        languageScores[note.language] = (languageScores[note.language] || 0) + confidence
+      }
+    }
+
+    // Find language with highest score
+    const sortedLanguages = Object.entries(languageScores)
+      .sort(([, a], [, b]) => b - a)
+
+    if (sortedLanguages.length > 0) {
+      const topLanguage = sortedLanguages[0][0] as SupportedLanguage
+      // Verify it's a supported language
+      if (['fr', 'en', 'es', 'de', 'fa'].includes(topLanguage)) {
+        return topLanguage
+      }
+    }
+
+    return 'en'
+  } catch (error) {
+    console.error('Error detecting user language:', error)
+    return 'en'
+  }
+}