feat(sidebar+assistant): filtre Recents/Sauvegardes (#99), pastille Deep Research (#100) et icone du bouton + (BUG-049)

frontend/locales/en.json

@@ -1545,6 +1545,8 @@
   "sidebar.file_icons": "Icons",
   "sidebar.filter_instant": "Instant search",
   "sidebar.filter_ai": "Filter AI history...",
+  "sidebar.filter_recent": "Filter recent files...",
+  "sidebar.filter_saved": "Filter saved searches...",
   "sidebar.filter_path": "Path filters",
   "sidebar.filter_placeholder": "Filter files...",
   "sidebar.filter_results_grouped": "Grouped results",
@@ -1849,7 +1851,7 @@
   "bookslm.soon": "Soon",
   "bookslm.ext_more_coming": "More options coming…",
   "bookslm.deep_research_prompt": "Perform an in-depth analysis of the request by breaking it into steps, searching for relevant information in the vault, cross-referencing them, and producing a structured summary with sources.",
-  "bookslm.deep_research_started": "Deep research started — enable Agent mode to use the tools.",
+  "bookslm.deep_research_started": "Deep Research enabled — add your question and send.",
   "bookslm.mode_general": "General",
   "bookslm.mode_directory": "Directory",
   "bookslm.mode_documents": "Documents",