Name a deleted target on its historical deliveries (closes #211)

Deleting a target soft deletes its row while its deliveries survive
in the per-webhook database, so the event log kept rendering the
history and lost the label: every historical row read ": delivered"
and the deliveries block was headed by an empty name.

loadTargetMap already loaded soft-deleted rows Unscoped for the
redactor half, then discarded them before building the view half.
It now builds both halves from every loaded row, and TargetView
carries a Deleted flag with a DisplayName that renders
"name (deleted)" — an operator debugging an old delivery needs to
know the target is gone, not just what it was called.

The views still come from NewTargetViews, so a deleted target's
configuration is masked by exactly the code that masks a live
one's. The widening is confined to this map, which feeds only
DeliveryView.Target on the event log page: the source detail
target list, the target edit form, the receiver and resubmit fan-out
and the delivery engine each resolve targets through their own
scoped queries, and the replay path keeps refusing a deleted target.

internal/delivery/target_config_view.go

@@ -23,21 +23,51 @@ type ConfigField struct {
 	Value string
 }
 
+// deletedNameSuffix marks the name of a target that no longer
+// exists. Deletes are soft and delivery history outlives the
+// target, so the event log shows names of targets that are gone;
+// an operator reading one needs to know it cannot be delivered
+// to, replayed to, or configured.
+const deletedNameSuffix = " (deleted)"
+
 // TargetView is the display-safe projection of a target for
 // the UI. It deliberately has no raw configuration field, so
 // no template — present or future — can render the stored
 // blob.
 type TargetView struct {
-	ID     string
-	Name   string
+	ID   string
+	Name string
+
+	// Deleted reports that this target's row is soft deleted.
+	// Only views built for historical display carry it set:
+	// every other projection is of a live row.
+	Deleted bool
+
 	Type   database.TargetType
 	Active bool
 	Config []ConfigField
 }
 
+// DisplayName is the name to render, marked when the target has
+// been deleted. Templates showing a name against historical data
+// must use it rather than Name, which stays the stored name.
+func (v TargetView) DisplayName() string {
+	if v.Deleted {
+		return v.Name + deletedNameSuffix
+	}
+
+	return v.Name
+}
+
 // NewTargetViews projects targets for rendering, replacing
 // each stored configuration blob with named, display-safe
 // fields.
+//
+// A soft-deleted row projects exactly as a live one does, minus
+// the deleted marker on its name: masking is a property of the
+// projection, not of the row's state, so a deleted target's
+// credential is as unreachable from a template as a live
+// target's.
 func NewTargetViews(
 	targets []database.Target,
 ) []TargetView {
@@ -47,11 +77,12 @@ func NewTargetViews(
 		t := &targets[i]
 
 		views = append(views, TargetView{
-			ID:     t.ID,
-			Name:   t.Name,
-			Type:   t.Type,
-			Active: t.Active,
-			Config: targetConfigFields(t),
+			ID:      t.ID,
+			Name:    t.Name,
+			Deleted: t.DeletedAt.Valid,
+			Type:    t.Type,
+			Active:  t.Active,
+			Config:  targetConfigFields(t),
 		})
 	}