Flag guests that no backup job covers

The guest table marks with "!" each guest that Proxmox's not-backed-up
list returns. The frame's bottom border shows the count, e.g.
"mainframe · 2 without backup job". This uses Proxmox's own answer, so
it also counts jobs that select guests by pool.

If the coverage call fails, the guests are still listed and a warning
says the coverage is unknown.

Closes #9

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/cv4pve_tui/app.py

@@ -659,6 +659,8 @@ class GuestApp(App):
         # bumped on every context switch; replies started earlier come from the old cluster
         self.generation = 0
         self.switching = False
+        self.context_name = ""
+        self.unprotected: set[int] = set()  # VMIDs no backup job covers
 
     CSS = """
     #guests_section {
@@ -679,6 +681,7 @@ class GuestApp(App):
         self.watch(self, "sub_title", self._show_context_frame)
         table = self.query_one("#guests", DataTable)
         table.add_columns(
+            "",  # "!" = no backup job covers the guest
             "VMID",
             "Name",
             "Type",
@@ -692,9 +695,13 @@ class GuestApp(App):
         self.action_reload()
 
     def _show_context_frame(self, sub_title: str) -> None:
-        self.query_one("#guests_section").border_subtitle = sub_title.removeprefix(
-            "context: "
-        )
+        self.context_name = sub_title.removeprefix("context: ")
+        self._update_frame()
+
+    def _update_frame(self) -> None:
+        n = len(self.unprotected & {g["vmid"] for g in self.guests.values()})
+        count = f" · {n} without backup job" if n else ""
+        self.query_one("#guests_section").border_subtitle = self.context_name + count
 
     @work(thread=True)
     def _show_context(self) -> None:
@@ -724,21 +731,26 @@ class GuestApp(App):
             table.coordinate_to_cell_key(table.cursor_coordinate).row_key.value
         ]
 
-    def _fill(self, guests: list[dict], gen: int) -> None:
+    def _fill(
+        self, guests: list[dict], gen: int, unprotected: set[int] | None = None
+    ) -> None:
         if gen != self.generation:  # listed before a context switch: old cluster
             return
+        self.unprotected = unprotected or set()
         table = self.query_one("#guests", DataTable)
         current = self._selected()
         table.clear()
         self.guests = {str(g["vmid"]): g for g in guests}
         for g in guests:
-            _add_plain(table, 
+            _add_plain(table,
+                "!" if g["vmid"] in self.unprotected else "",
                 g["vmid"], g["name"], g["type"], g["node"], g["status"],
                 g.get("maxcpu", "-"), _scaled(g.get("maxmem"), 2**20), _scaled(g.get("maxdisk"), 2**30),
                 key=str(g["vmid"]),
             )  # fmt: skip
         if current and str(current["vmid"]) in self.guests:
             table.move_cursor(row=table.get_row_index(str(current["vmid"])))
+        self._update_frame()
 
     def _reload(self, acted: dict | None = None) -> None:
         """Runs in a worker thread. `acted` gets its live status: the listing lags."""
@@ -751,7 +763,16 @@ class GuestApp(App):
         except Exception as exc:  # noqa: BLE001 - any failure must reach the user, not kill the app
             self.call_from_thread(self.notify, _message(exc), severity="error")
             return
-        self.call_from_thread(self._fill, guests, gen)
+        unprotected = None
+        try:
+            unprotected = cli.not_backed_up()
+        except Exception as exc:  # noqa: BLE001 - the listing still works without it
+            self.call_from_thread(
+                self.notify,
+                f"backup coverage unknown: {_message(exc)}",
+                severity="warning",
+            )
+        self.call_from_thread(self._fill, guests, gen, unprotected)
 
     def action_reload(self) -> None:
         if self.switching: