feat(FN-1153): add cross-tab locks for AI planning sessions

- Bump SQLite schema to v19 with ai_sessions lock columns and lock index, and align migration coverage in core DB tests
- Extend AiSessionStore with acquire/release/force lock APIs, stale lock cleanup, and lock metadata in ai_session update summaries
- Enforce lock checks on planning, subtask, and mission interview mutation routes with 409 conflict responses while keeping stream reads unaffected
- Add frontend tab identity + useSessionLock hook and wire Planning, Subtask, and Mission modals to pass tabId, show lock overlay, and support Take Control
- Expand dashboard route/e2e and modal tests to validate lock enforcement, lock handoff, and lock-aware session reentry behavior

packages/dashboard/app/utils/getSessionTabId.ts

@@ -0,0 +1,25 @@
+const SESSION_TAB_ID_KEY = "fusion-tab-id";
+
+function createTabId(): string {
+  const cryptoApi = globalThis.crypto;
+  if (cryptoApi && typeof cryptoApi.randomUUID === "function") {
+    return cryptoApi.randomUUID();
+  }
+
+  return `tab-${Date.now()}-${Math.random().toString(36).slice(2, 10)}`;
+}
+
+export function getSessionTabId(): string {
+  if (typeof window === "undefined") {
+    return "server-tab";
+  }
+
+  const existing = window.sessionStorage.getItem(SESSION_TAB_ID_KEY);
+  if (existing) {
+    return existing;
+  }
+
+  const next = createTabId();
+  window.sessionStorage.setItem(SESSION_TAB_ID_KEY, next);
+  return next;
+}