feat: add extension scaffolding

Manifest, package.json, tsconfig, webpack config, popup HTML shell,
WASM type declarations, and .gitignore entries for the Chrome MV3 extension.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

extension/manifest.json

@@ -0,0 +1,28 @@
+{
+  "manifest_version": 3,
+  "name": "idfoto",
+  "version": "0.1.0",
+  "description": "Two-factor encrypted password manager",
+  "permissions": ["storage", "activeTab", "clipboardWrite"],
+  "host_permissions": ["<all_urls>"],
+  "background": {
+    "service_worker": "service-worker.js",
+    "type": "module"
+  },
+  "action": {
+    "default_popup": "popup.html",
+    "default_icon": {
+      "16": "icons/icon-16.png",
+      "48": "icons/icon-48.png",
+      "128": "icons/icon-128.png"
+    }
+  },
+  "content_scripts": [{
+    "matches": ["<all_urls>"],
+    "js": ["content.js"],
+    "run_at": "document_idle"
+  }],
+  "content_security_policy": {
+    "extension_pages": "script-src 'self' 'wasm-unsafe-eval'; object-src 'self'"
+  }
+}