feat(PBI-76): user-settings zustand store with optimistic flow

Hydrate from prop (SSR-correct), setPref via path with optimistic
update + rollback on server error, applyServerPatch for SSE-driven
cross-tab updates. Demo accounts skip server-write entirely.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

stores/user-settings/selectors.ts

@@ -0,0 +1,23 @@
+import type { UserSettings } from '@/lib/user-settings'
+
+interface StateLike {
+  entities: { settings: UserSettings }
+  context: { hydrated: boolean; isDemo: boolean }
+}
+
+export const selectSprintBacklogPrefs = (s: StateLike) =>
+  s.entities.settings.views?.sprintBacklog ?? {}
+
+export const selectPbiListPrefs = (s: StateLike) =>
+  s.entities.settings.views?.pbiList ?? {}
+
+export const selectStoryPanelPrefs = (s: StateLike) =>
+  s.entities.settings.views?.storyPanel ?? {}
+
+export const selectJobsColumnPrefs = (key: string) => (s: StateLike) =>
+  s.entities.settings.views?.jobsColumns?.[key] ?? { kinds: [], statuses: [] }
+
+export const selectDevToolsPrefs = (s: StateLike) =>
+  s.entities.settings.devTools ?? {}
+
+export const selectHydrated = (s: StateLike) => s.context.hydrated

stores/user-settings/store.ts

@@ -0,0 +1,116 @@
+import { create } from 'zustand'
+import { immer } from 'zustand/middleware/immer'
+
+import {
+  DEFAULT_USER_SETTINGS,
+  mergeSettings,
+  type UserSettings,
+} from '@/lib/user-settings'
+import { updateUserSettingsAction } from '@/actions/user-settings'
+
+type SettingsPath = readonly (string | number)[]
+
+interface PendingMutation {
+  id: number
+  prev: UserSettings
+}
+
+interface UserSettingsState {
+  entities: { settings: UserSettings }
+  context: {
+    hydrated: boolean
+    isDemo: boolean
+  }
+  pendingMutations: Record<number, PendingMutation>
+}
+
+interface UserSettingsActions {
+  hydrate: (initial: UserSettings, isDemo: boolean) => void
+  setPref: (path: SettingsPath, value: unknown) => Promise<void>
+  applyServerPatch: (patch: Partial<UserSettings>) => void
+}
+
+let nextMutationId = 1
+
+function patchFromPath(path: SettingsPath, value: unknown): Partial<UserSettings> {
+  if (path.length === 0) {
+    if (value && typeof value === 'object' && !Array.isArray(value)) {
+      return value as Partial<UserSettings>
+    }
+    return {}
+  }
+  const out: Record<string, unknown> = {}
+  let cursor: Record<string, unknown> = out
+  for (let i = 0; i < path.length - 1; i++) {
+    const key = String(path[i])
+    cursor[key] = {}
+    cursor = cursor[key] as Record<string, unknown>
+  }
+  cursor[String(path[path.length - 1])] = value
+  return out as Partial<UserSettings>
+}
+
+export const useUserSettingsStore = create<UserSettingsState & UserSettingsActions>()(
+  immer((set, get) => ({
+    entities: { settings: DEFAULT_USER_SETTINGS },
+    context: { hydrated: false, isDemo: false },
+    pendingMutations: {},
+
+    hydrate: (initial, isDemo) => {
+      set((draft) => {
+        draft.entities.settings = initial as UserSettings
+        draft.context.hydrated = true
+        draft.context.isDemo = isDemo
+      })
+    },
+
+    applyServerPatch: (patch) => {
+      set((draft) => {
+        draft.entities.settings = mergeSettings(
+          draft.entities.settings as UserSettings,
+          patch,
+        ) as UserSettings
+      })
+    },
+
+    setPref: async (path, value) => {
+      const patch = patchFromPath(path, value)
+
+      // Demo: lokale merge zonder server-call.
+      if (get().context.isDemo) {
+        set((draft) => {
+          draft.entities.settings = mergeSettings(
+            draft.entities.settings as UserSettings,
+            patch,
+          ) as UserSettings
+        })
+        return
+      }
+
+      const mutationId = nextMutationId++
+      const prev = get().entities.settings as UserSettings
+
+      // Optimistic.
+      set((draft) => {
+        draft.entities.settings = mergeSettings(
+          draft.entities.settings as UserSettings,
+          patch,
+        ) as UserSettings
+        draft.pendingMutations[mutationId] = { id: mutationId, prev }
+      })
+
+      const result = await updateUserSettingsAction(patch)
+
+      set((draft) => {
+        delete draft.pendingMutations[mutationId]
+        if ('error' in result) {
+          // Rollback alleen als geen latere mutatie de waarde alweer heeft overschreven.
+          draft.entities.settings = prev as UserSettings
+        } else {
+          // Settle: server-merge is autoritatief.
+          draft.entities.settings = result.settings as UserSettings
+        }
+      })
+    },
+  })),
+)