fix(20): add SNMP profiles settings link and device_count to profile list

Adds SNMP Device Profiles card to SettingsPage for discoverability.
Adds device_count correlated subquery to profile list SQL and schema
field so the frontend profile cards show accurate device counts.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/routers/snmp_profiles.py

@@ -79,11 +79,17 @@ async def list_profiles(
 
     result = await db.execute(
         text("""
-            SELECT id, tenant_id, name, description, sys_object_id, vendor,
-                   category, is_system, created_at, updated_at
-            FROM snmp_profiles
-            WHERE tenant_id = :tenant_id OR tenant_id IS NULL
-            ORDER BY is_system DESC, name ASC
+            SELECT sp.id, sp.tenant_id, sp.name, sp.description, sp.sys_object_id, sp.vendor,
+                   sp.category, sp.is_system, sp.created_at, sp.updated_at,
+                   COALESCE(dc.device_count, 0) AS device_count
+            FROM snmp_profiles sp
+            LEFT JOIN LATERAL (
+                SELECT COUNT(*) AS device_count
+                FROM devices d
+                WHERE d.snmp_profile_id = sp.id
+            ) dc ON true
+            WHERE sp.tenant_id = :tenant_id OR sp.tenant_id IS NULL
+            ORDER BY sp.is_system DESC, sp.name ASC
         """),
         {"tenant_id": str(tenant_id)},
     )

backend/app/schemas/snmp_profile.py

@@ -75,6 +75,7 @@ class SNMPProfileResponse(BaseModel):
     vendor: Optional[str] = None
     category: Optional[str] = None
     is_system: bool
+    device_count: int = 0
     created_at: datetime
     updated_at: datetime
 

frontend/src/components/settings/SettingsPage.tsx

@@ -167,6 +167,23 @@ export function SettingsPage() {
         </div>
       )}
 
+      {/* SNMP Profiles */}
+      {isTenantAdmin(user) && (
+        <div className="rounded-lg border border-border bg-panel px-4 py-3 space-y-1">
+          <SectionHeader icon={Monitor} title="SNMP Profiles" />
+          <Link
+            to="/settings/snmp-profiles"
+            className="flex items-center justify-between py-2 px-1 rounded hover:bg-elevated/30 transition-colors group"
+          >
+            <div>
+              <span className="text-sm text-text-primary">SNMP Device Profiles</span>
+              <p className="text-xs text-text-muted">Manage OID collection profiles, upload MIBs, test against live devices</p>
+            </div>
+            <ChevronRight className="h-4 w-4 text-text-muted group-hover:text-text-primary transition-colors" />
+          </Link>
+        </div>
+      )}
+
       {/* Maintenance — super_admin only */}
       {isSuperAdmin(user) && (
         <div className="rounded-lg border border-border bg-panel px-4 py-3 space-y-1">