feat(orchestrator): authoritative failure-count badge endpoint (DEBT-042)

New GET /api/v1/orchestrator/events/stats?since=1h&success=false&kind=...
backed by repo.count_orchestrator_failures(since_ts, kind), which
counts failed rows across both orchestrator_events and
orchestrator_emails since the cutoff.

Window parser accepts ^\d+[smhd]$, capped at 7d. Today only
success=false is accepted on this surface so the endpoint isn't
accidentally repurposed before the next consumer is properly
designed.

Orchestrator.tsx polls the endpoint on mount + every 30 s and
renders the authoritative DB-derived count instead of deriving from
the in-memory SSE buffer + one paginated page (which silently
excluded failures older than the local window).

decnet/web/db/repository.py

@@ -1131,6 +1131,17 @@ class BaseRepository(ABC):
         """Total orchestrator-event rows, optionally filtered by kind."""
         raise NotImplementedError
 
+    async def count_orchestrator_failures(
+        self,
+        *,
+        since_ts: Any,
+        kind: Optional[str] = None,
+    ) -> int:
+        """Count failed orchestrator activity since *since_ts*, across
+        both event + email tables. Backs the dashboard's failure-count
+        badge (DEBT-042)."""
+        raise NotImplementedError
+
     async def prune_orchestrator_events(self, per_dst_cap: int = 10000) -> int:
         """Trim per-``dst_decky_uuid`` rows to a cap. Returns deleted count.
 

decnet/web/db/sqlmodel_repo/orchestrator.py

@@ -60,6 +60,46 @@ class OrchestratorMixin(_MixinBase):
             result = await session.execute(stmt)
             return result.scalar() or 0
 
+    async def count_orchestrator_failures(
+        self,
+        *,
+        since_ts: datetime,
+        kind: Optional[str] = None,
+    ) -> int:
+        """Count failed orchestrator activity since *since_ts*, across
+        both ``orchestrator_events`` (traffic / file) and
+        ``orchestrator_emails`` (email).
+
+        Backs the dashboard's failure-count badge — see DEBT-042. The
+        in-memory window the badge previously computed against was
+        bounded by the SSE-buffer + paginated page, so failures older
+        than the local window read low. This is the authoritative count.
+        """
+        async with self._session() as session:
+            ev_stmt = (
+                select(func.count()).select_from(OrchestratorEvent)
+                .where(
+                    col(OrchestratorEvent.success).is_(False),
+                    OrchestratorEvent.ts >= since_ts,
+                )
+            )
+            if kind in ("traffic", "file"):
+                ev_stmt = ev_stmt.where(OrchestratorEvent.kind == kind)
+            em_stmt = (
+                select(func.count()).select_from(OrchestratorEmail)
+                .where(
+                    col(OrchestratorEmail.success).is_(False),
+                    OrchestratorEmail.ts >= since_ts,
+                )
+            )
+            ev_count = 0
+            em_count = 0
+            if kind in (None, "traffic", "file"):
+                ev_count = (await session.execute(ev_stmt)).scalar() or 0
+            if kind in (None, "email"):
+                em_count = (await session.execute(em_stmt)).scalar() or 0
+            return ev_count + em_count
+
     async def prune_orchestrator_events(self, per_dst_cap: int = 10000) -> int:
         """Trim per-dst rows to *per_dst_cap*, oldest-first. Returns deleted count."""
         deleted = 0