Update extension system and database migrations

Changes:
- Added CLAUDE.md with project instructions
- Updated extension manifest bindings (TypeScript)
- Regenerated database migrations (consolidated into single migration)
- Updated haex schema with table name handling
- Enhanced extension manager and manifest handling in Rust
- Updated extension store in frontend
- Updated vault.db

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src-tauri/database/schemas/haex.ts

@@ -47,11 +47,12 @@ export const haexExtensions = sqliteTable(
     version: text().notNull(),
     author: text(),
     description: text(),
-    entry: text().notNull().default('index.html'),
+    entry: text().default('index.html'),
     homepage: text(),
     enabled: integer({ mode: 'boolean' }).default(true),
     icon: text(),
     signature: text().notNull(),
+    single_instance: integer({ mode: 'boolean' }).default(false),
   }),
   (table) => [
     // UNIQUE constraint: Pro Developer (public_key) kann nur eine Extension mit diesem Namen existieren