Support issue identifiers (PAP-39) in URLs and prefer them throughout

Backend:
- Add router.param middleware in issues, activity, and agents routes to
  resolve identifiers (e.g. PAP-39) to UUIDs before handlers run
- Simplify GET /issues/:id now that param middleware handles resolution
- Include identifier in getAncestors response and issuesForRun query
- Add identifier field to IssueAncestor shared type

Frontend:
- Update all issue navigation links across 15+ files to use
  issue.identifier ?? issue.id instead of bare UUIDs
- Add URL redirect in IssueDetail: navigating via UUID automatically
  replaces the URL with the human-readable identifier
- Fix childIssues filter to use issue.id (UUID) instead of URL param
  so it works correctly with identifier-based URLs
- Add issueUrl() utility in lib/utils.ts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/services/issues.ts

@@ -574,7 +574,7 @@ export function issueService(db: Db) {
 
     getAncestors: async (issueId: string) => {
       const raw: Array<{
-        id: string; title: string; description: string | null;
+        id: string; identifier: string | null; title: string; description: string | null;
         status: string; priority: string;
         assigneeAgentId: string | null; projectId: string | null; goalId: string | null;
       }> = [];
@@ -584,14 +584,14 @@ export function issueService(db: Db) {
       while (currentId && !visited.has(currentId) && raw.length < 50) {
         visited.add(currentId);
         const parent = await db.select({
-          id: issues.id, title: issues.title, description: issues.description,
+          id: issues.id, identifier: issues.identifier, title: issues.title, description: issues.description,
           status: issues.status, priority: issues.priority,
           assigneeAgentId: issues.assigneeAgentId, projectId: issues.projectId,
           goalId: issues.goalId, parentId: issues.parentId,
         }).from(issues).where(eq(issues.id, currentId)).then(r => r[0] ?? null);
         if (!parent) break;
         raw.push({
-          id: parent.id, title: parent.title, description: parent.description ?? null,
+          id: parent.id, identifier: parent.identifier ?? null, title: parent.title, description: parent.description ?? null,
           status: parent.status, priority: parent.priority,
           assigneeAgentId: parent.assigneeAgentId ?? null,
           projectId: parent.projectId ?? null, goalId: parent.goalId ?? null,