feat(web): add kanban board + list view + filtering to My Issues page

Upgrade /my-issues from a simple accordion to a full-featured view
matching /issues — kanban board, list view, status/priority filtering,
sorting, and display settings, scoped to the user's own issues.

Key changes:
- Extract view store factory (createIssueViewStore) using zustand v5
  vanilla createStore + React Context for shared component reuse
- Create ViewStoreProvider + useViewStore/useViewStoreApi hooks
- Decouple BoardView, BoardColumn, BoardCard, ListView from global
  useIssueViewStore — they now read from context
- New independent persisted store for /my-issues (multica_my_issues_view)
- Simplified MyIssuesHeader (no assignee/creator filters)
- Pre-filter logic: assigned to me ∪ my agents ∪ created by me
- Generalize workspace sync to clear filters on all registered stores
- Fix existing debt: text-[10px] → text-xs, w-44 → w-auto, reduce
  unnecessary selector subscriptions in both headers

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

apps/web/features/issues/components/board-card.tsx

@@ -13,7 +13,8 @@ import { useIssueStore } from "@/features/issues/store";
 import { PriorityIcon } from "./priority-icon";
 import { PriorityPicker, AssigneePicker, DueDatePicker } from "./pickers";
 import { PRIORITY_CONFIG } from "@/features/issues/config";
-import { useIssueViewStore, type CardProperties } from "@/features/issues/stores/view-store";
+import type { CardProperties } from "@/features/issues/stores/view-store";
+import { useViewStore } from "@/features/issues/stores/view-store-context";
 
 function formatDate(date: string): string {
   return new Date(date).toLocaleDateString("en-US", {
@@ -42,7 +43,7 @@ export const BoardCardContent = memo(function BoardCardContent({
   issue: Issue;
   editable?: boolean;
 }) {
-  const storeProperties = useIssueViewStore((s) => s.cardProperties);
+  const storeProperties = useViewStore((s) => s.cardProperties);
   const priorityCfg = PRIORITY_CONFIG[issue.priority];
 
   const handleUpdate = useCallback(