Initial implementation of vault-os

Complete implementation across all 13 phases:

- vault-core: types, YAML frontmatter parsing, entity classification,
  filesystem ops, config, prompt composition, validation, search
- vault-watch: filesystem watcher with daemon write filtering, event
  classification
- vault-scheduler: cron engine, process executor, task runner with
  retry logic and concurrency limiting
- vault-api: Axum REST API (15 route modules), WebSocket with broadcast,
  AI assistant proxy, validation, templates
- Dashboard: React + TypeScript + Tailwind v4 with kanban, CodeMirror
  editor, dynamic view system, AI chat sidebar
- Nix flake with dev shell and NixOS module
- Graceful shutdown, inotify overflow recovery, tracing instrumentation

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

dashboard/vite.config.ts

@@ -0,0 +1,13 @@
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+import tailwindcss from '@tailwindcss/vite'
+
+export default defineConfig({
+  plugins: [react(), tailwindcss()],
+  server: {
+    proxy: {
+      '/api': 'http://127.0.0.1:8080',
+      '/ws': { target: 'ws://127.0.0.1:8080', ws: true },
+    },
+  },
+})