feat(v4.0): Library tabs + Sidebar OAuth badge + Sharing routes

app/routers/library.py: /api/library/recents|favorites|shared|published|private|workspace
app/routers/sharing.py: /api/pages/{id}/share|publish + page_shares
app/templates/base.html: OAuth badge 🦎/🐙, '→ Library' buttons
app/templates/library.html: page avec tabs + filtres source
app/routers/dashboard.py: auth_method + github_linked dans context
tests/test_app.py: tests library + sharing + recents

tests/test_app.py

@@ -209,7 +209,8 @@ def test_db_tables_exist(client):
                     "collections", "collection_pages", "collection_views",
                     "collection_properties", "workspaces", "workspace_members",
                     "comments", "page_history", "favorites",
-                    "database_templates", "page_templates"}
+                    "database_templates", "page_templates",
+                    "page_shares", "recents"}
         assert required <= names