Add dashboard summary tiles

Shows rider count, activities imported in the last 7 days, 7-day
sync success rate, and how many riders currently need attention,
right above the rider list where an admin looks first.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/db/repositories.py

@@ -1,13 +1,14 @@
 from dataclasses import dataclass
 from datetime import datetime
 
-from sqlalchemy import and_, or_, select
+from sqlalchemy import and_, func, or_, select
 from sqlalchemy.exc import IntegrityError
 from sqlalchemy.orm import Session
 
 from app.db.models import (
     Activity,
     ActivityStatus,
+    HealthState,
     SchedulerSettings,
     SyncRun,
     SyncRunStatus,
@@ -19,6 +20,15 @@ from app.db.models import (
 _SCHEDULER_SETTINGS_ID = 1
 
 
+@dataclass(frozen=True)
+class DashboardSummary:
+    rider_total: int
+    rider_enabled: int
+    imported_recent: int
+    success_rate_recent: float | None
+    action_required_count: int
+
+
 @dataclass(frozen=True)
 class UserDashboardRow:
     id: int
@@ -78,6 +88,39 @@ class UserRepository:
             ))
         return rows
 
+    def dashboard_summary(self, *, since: datetime) -> DashboardSummary:
+        rider_total = self.session.scalar(select(func.count()).select_from(SyncUser)) or 0
+        rider_enabled = self.session.scalar(
+            select(func.count()).select_from(SyncUser).where(SyncUser.enabled.is_(True))
+        ) or 0
+        action_required_count = self.session.scalar(
+            select(func.count()).select_from(SyncUser).where(SyncUser.health_state == HealthState.ACTION_REQUIRED)
+        ) or 0
+        imported_recent = self.session.scalar(
+            select(func.coalesce(func.sum(SyncRun.imported_count), 0)).where(SyncRun.started_at >= since)
+        ) or 0
+
+        finished_runs = list(
+            self.session.scalars(
+                select(SyncRun).where(SyncRun.started_at >= since, SyncRun.finished_at.is_not(None))
+            )
+        )
+        if finished_runs:
+            successful = sum(
+                1 for run in finished_runs if run.status in (SyncRunStatus.SUCCESS, SyncRunStatus.PARTIAL)
+            )
+            success_rate_recent = (successful / len(finished_runs)) * 100
+        else:
+            success_rate_recent = None
+
+        return DashboardSummary(
+            rider_total=rider_total,
+            rider_enabled=rider_enabled,
+            imported_recent=imported_recent,
+            success_rate_recent=success_rate_recent,
+            action_required_count=action_required_count,
+        )
+
 
 class ActivityRepository:
     def __init__(self, session: Session) -> None: