feat(v3): migrate workspace to API, Tauri desktop, and v3 crates; remove legacy MCP stack

- Add apps/api, desktop Tauri shell, domain/application/crypto/device-auth/infrastructure-db
- Replace desktop-daemon vault integration; drop secrets-core and secrets-mcp*
- Ignore apps/desktop/dist and generated Tauri icons; document icon/dist steps in AGENTS.md
- Apply rustfmt; fix clippy (collapsible_if, HTTP method as str)

apps/desktop/src-tauri/tauri.conf.json

@@ -0,0 +1,31 @@
+{
+  "$schema": "https://schema.tauri.app/config/2",
+  "productName": "Secrets",
+  "version": "3.0.0",
+  "identifier": "dev.refining.secrets",
+  "build": {
+    "beforeDevCommand": "",
+    "beforeBuildCommand": "",
+    "frontendDist": "../dist"
+  },
+  "app": {
+    "windows": [
+      {
+        "title": "Secrets",
+        "width": 420,
+        "height": 400,
+        "minWidth": 420,
+        "minHeight": 400,
+        "resizable": true,
+        "titleBarStyle": "overlay",
+        "hiddenTitle": true
+      }
+    ],
+    "security": {
+      "csp": null
+    }
+  },
+  "bundle": {
+    "active": false
+  }
+}