fix: show a generic "App Blocked" shield instead of mis-attributing a rule

The shield titled itself with the first enabled rule whose selection
contained the app, regardless of whether that rule was the one actually
blocking. When several rules covered the same app (e.g. a dormant
schedule + the active limit) it named the wrong rule.

Drop the rule-name lookup entirely: every shield now carries a generic
"App Blocked" title. Open-limit shields keep their functional detail
(running count + "Open (N left)" button) beneath that title. The
text-only decision moves into a pure, unit-tested ShieldPresentation in
Shared/, and the now-dead ShieldLookup.snapshot(containingApplication:)
is removed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Shared/ShieldLookup.swift

@@ -29,16 +29,4 @@ enum ShieldLookup {
                 .categoryTokens.contains(token)
         }
     }
-
-    /// Any enabled rule whose selection includes the application (for naming
-    /// plain blocked shields).
-    static func snapshot(
-        containingApplication token: ApplicationToken, in snapshots: [RuleSnapshot]
-    ) -> RuleSnapshot? {
-        snapshots.first { snapshot in
-            guard snapshot.isEnabled else { return false }
-            return AppSelectionCodec.decode(snapshot.selectionData)
-                .applicationTokens.contains(token)
-        }
-    }
 }