feat(app): filter the sidebar by project (#3563)

The sidebar can be pinned to a set of hosts or to a set of labels, but
not to a set of projects. If you keep many projects on one host, the
project is the filter you want.

Add a Project page to the sidebar display menu, next to Host. It
multi-selects projects, and an empty selection means every project.

Apply the filter at two points. Project grouping reads the projects
array, but Status grouping builds its rows from the workspace entries.
A filter applied to only one of the two leaves the other mode
unfiltered.

Apply nothing when a stored selection names no visible project. The
project list is narrowed by the host filter, and it is empty before any
host connects, so dropping keys that do not match would destroy the
selection on every cold start.

Count the project filter in the sidebar header gate. Pinning every chat
in a project drops that project from the unpinned list. Filtering to
that project then removed the header, and the header carries the display
menu, which is the only way back to the Project page.

Generalise the label filter empty state to all sidebar filters, and move
its strings out of the labels namespace.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

packages/app/src/i18n/resources/pt-BR.ts

@@ -1010,8 +1010,6 @@ export const ptBR: TranslationResources = {
     },
     filter: {
       clear: "Limpar filtro",
-      noMatchesTitle: "Nenhum espaço de trabalho corresponde",
-      noMatchesDescription: "Altere ou limpe o filtro de etiquetas para ver espaços de trabalho.",
     },
     manage: {
       open: "Gerenciar etiquetas…",
@@ -1067,6 +1065,15 @@ export const ptBR: TranslationResources = {
         label: "Host",
         all: "Todos os hosts",
       },
+      projectFilter: {
+        label: "Projeto",
+        all: "Todos os projetos",
+      },
+    },
+    filterEmpty: {
+      title: "Nenhum espaço de trabalho corresponde",
+      description: "Altere ou limpe os filtros da barra lateral para ver espaços de trabalho.",
+      clear: "Limpar filtros",
     },
     pinned: {
       title: "Fixados",