refactor: convert to bun workspaces monorepo

- Move web app into apps/web/
- Create packages/shared/ with shared types
- Create plugins/decky-vault/ scaffold
- Root package.json manages workspaces only

plugins/decky-vault/src/index.tsx

@@ -0,0 +1,32 @@
+import { DeckyVaultImportV1 } from "@deckyvault/shared"
+
+interface PluginSettings {
+  apiKey: string
+  autoRecord: boolean
+  exportPath: string
+}
+
+let settings: PluginSettings = {
+  apiKey: "",
+  autoRecord: false,
+  exportPath: "/home/deck/Downloads",
+}
+
+export default {
+  name: "DeckyVault",
+  content: () => {
+    // Main plugin UI — will be implemented in a future phase
+    return <div>DeckyVault Plugin</div>
+  },
+  onSettingUpdate: (newSettings: Partial<PluginSettings>) => {
+    settings = { ...settings, ...newSettings }
+  },
+  onGameSessionStart: (appId: number) => {
+    DeckyPlugin.log(`[DeckyVault] Game started: ${appId}`)
+    // Future: start MangoHud monitoring
+  },
+  onGameSessionEnd: (appId: number) => {
+    DeckyPlugin.log(`[DeckyVault] Game stopped: ${appId}`)
+    // Future: stop monitoring, prompt export/upload
+  },
+}