feat(browser): implement browser extension for sending files to DocuElevate

- Add complete browser extension with popup UI and background workers
- Support Chrome, Firefox, Edge, and other Chromium-based browsers
- Include context menu integration for quick file sending
- Add comprehensive documentation for users and administrators
- Update main README and API docs to include browser extension
- Implement secure configuration storage in browser extension storage
- Add SSRF-protected URL upload endpoint integration

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

browser-extension/manifest.json

@@ -0,0 +1,38 @@
+{
+  "manifest_version": 3,
+  "name": "DocuElevate - Send to Document Processor",
+  "version": "1.0.0",
+  "description": "Send files from your browser directly to DocuElevate for processing",
+  "permissions": [
+    "activeTab",
+    "storage",
+    "contextMenus",
+    "notifications"
+  ],
+  "host_permissions": [],
+  "action": {
+    "default_popup": "popup/popup.html",
+    "default_icon": {
+      "16": "icons/icon16.png",
+      "32": "icons/icon32.png",
+      "48": "icons/icon48.png",
+      "128": "icons/icon128.png"
+    }
+  },
+  "icons": {
+    "16": "icons/icon16.png",
+    "32": "icons/icon32.png",
+    "48": "icons/icon48.png",
+    "128": "icons/icon128.png"
+  },
+  "background": {
+    "service_worker": "scripts/background.js"
+  },
+  "content_scripts": [
+    {
+      "matches": ["<all_urls>"],
+      "js": ["scripts/content.js"],
+      "run_at": "document_idle"
+    }
+  ]
+}