feat: icon-only toolbar, versioning fixes, history modal, PanelRight repositioning

- Toolbar: remove text labels from all icon buttons (AI, Save, Preview, Convert)
  all buttons now icon-only with title tooltip for accessibility
- Toolbar: reposition PanelRight (info panel toggle) to far right after three-dot menu
- Versioning: decouple getNoteHistory/restoreNoteVersion from global userAISettings.noteHistory
  now checks note.historyEnabled directly — unblocks manual per-note history
- Versioning: add 'Sauvegarder cette version' button in Versions tab of info panel
  calls commitNoteHistory with visual feedback (spinner → success state)
- note-document-info-panel: import commitNoteHistory, add isSavingVersion state
- notes.ts: fix double guard that silently blocked all history operations

architectural-grid (5)/.env.example

@@ -0,0 +1,9 @@
+# GEMINI_API_KEY: Required for Gemini AI API calls.
+# AI Studio automatically injects this at runtime from user secrets.
+# Users configure this via the Secrets panel in the AI Studio UI.
+GEMINI_API_KEY="MY_GEMINI_API_KEY"
+
+# APP_URL: The URL where this applet is hosted.
+# AI Studio automatically injects this at runtime with the Cloud Run service URL.
+# Used for self-referential links, OAuth callbacks, and API endpoints.
+APP_URL="MY_APP_URL"