feat(tabs): add multi-account tab support with isolated sessions}
- Add tab-manager.mjs with full tab lifecycle (create, remove, switch, persist/restore state) using separate webview partitions per tab - Replace single static webview with dynamically created webviews in a tab bar UI, each with its own session isolation - Add tab bar HTML structure and CSS styling (tab strip, active state, close buttons, add-tab button) - Extract per-webview event handling from event/handler.mjs into tab-manager.mjs for per-tab navigation and dark mode injection - Add proxy properties on global.p3x.onenote for webview/domReady to maintain backward compatibility with existing code - Update multi-actions.mjs to apply dark mode invert across all tab webviews, and add null-safety guards for webview references - Update ipc/handler.mjs to delegate URL loading to tab manager and re-render tab bar on language change - Update load.mjs to initialize tab manager, wire bottom bar buttons through active-webview getter, and remove old single-webview setup - Migrate old single-webview persisted URL to new tabs format on first run - Auto-detect account email from OAuth callback to label tabs - Add tab-related translation keys (addTab, closeTab, personal, corporate, cannotCloseLastTab, confirmClose) across all 30 locales - Bump version to v2026.4.116 across package.json, README, artifacts, and changelogs