Add multi-account OAuth, Obsidian integration, product assets, and test tooling

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

test-gmail-search.mjs

@@ -0,0 +1,13 @@
+import { searchMessages, getProfile } from './dist/imap.js';
+
+async function main() {
+  try {
+    console.log('Profile:', await getProfile('gmail'));
+    const results = await searchMessages('test', 5, 'gmail');
+    console.log('Results:', JSON.stringify(results, null, 2));
+  } catch (err) {
+    console.error('ERROR:', err.message);
+    console.error(err.stack);
+  }
+}
+main();