fix: tolerate non-string YAML list elements when parsing tickets

YAML values like '1.0' (unquoted) parse as double, not String.
Changed parseStringList to use string interpolation ('$e') instead
of 'e as String', so numeric YAML scalars in labels/milestones
don't crash ticket parsing.

Also quote all '1.0' label values in existing ticket files so they
are unambiguously strings in YAML.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.project/kanban/backlog/DEW-0028.md

@@ -6,7 +6,7 @@ created: 2026-04-25T19:53:27.907063Z
 milestones:
   - 1.0.0
 labels:
-  - 1.0
+  - "1.0"
 ---
 
 Publish all four packages to pub.dev in dependency order, then tag the release.

packages/kanban/lib/src/ticket.dart

@@ -170,7 +170,7 @@ class Ticket {
 
     List<String> parseStringList(String key) {
       final raw = fm[key] as YamlList?;
-      return raw?.map((e) => e as String).toList() ?? const [];
+      return raw?.map((e) => '$e').toList() ?? const [];
     }
 
     return Ticket(