feat(PBI-76): migrate cookie-based prefs to user-settings (Phase 2) (#189)

* feat(PBI-76): extend UserSettings schema with layout

Adds layout.splitPanePositions and layout.activeSprints. These will
hold values currently kept in client-side and server-side cookies
(Phase 2). Two new tests cover the shape.

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

* feat(PBI-76): migrate SplitPane positions to user-settings store

Outside of a drag the store is the source of truth (cross-tab
updates flow in for free). During a drag we keep splits in local
state so mousemove does not round-trip through the store. On
mouseup we persist the final splits via setPref. Removes
document.cookie reads/writes — cookieKey is reused as the
store-key for backwards compat.

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

* feat(PBI-76): resolveActiveSprint reads from User.settings

lib/active-sprint:
- New helpers: getActiveSprintIdFromSettings, setActiveSprintInSettings,
  clearActiveSprintInSettings — all read/write user.settings.layout.activeSprints.
- resolveActiveSprint(productId, userId) — userId now required, falls back
  to first OPEN, then most recent CLOSED sprint.
- Cookie helpers (getActiveSprintIdFromCookie/setActiveSprintCookie/
  clearActiveSprintCookie) removed.

Callers updated to pass session.userId. The cookie-based fallback path
is gone — `actions/active-sprint.ts` and `actions/sprints.ts` will be
updated in the next commit (T-917).

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

* feat(PBI-76): rewrite setActiveSprint callers to use settings

setActiveSprintAction, syncActiveSprintCookieAction, and the two
sprint-creation paths in actions/sprints.ts now write through
setActiveSprintInSettings (which also emits pg_notify for cross-tab
sync) instead of dropping a cookie. The action names keep the
'cookie' suffix in the user-visible API for now — clean rename can
come later.

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

* feat(PBI-76): migration helper v2 — handle legacy cookies

Bumps marker version to 'v2'. buildMigrationPatch now also scans
document.cookie for `sp:*` (split-pane positions) and
`active_sprint_*` (active sprint per product) and lifts them into
layout.splitPanePositions / layout.activeSprints. clearLegacyStorage
replaces clearLegacyLocalStorage and clears both keys and cookies.
clearLegacyLocalStorage stays as a deprecated alias so the bridge
upgrade is a single rename.

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

* test(PBI-76): align tests with new SplitPane and active-sprint flow

- split-pane.test.tsx: seed positions via Zustand store instead of
  document.cookie; mock @/actions/user-settings so the prisma client
  is not transitively initialised in jsdom.
- backlog-split-pane.test.tsx: same action mock.
- sprint-dates.test.ts: add user.findUnique/update + $executeRaw
  mocks because createSprintAction now writes to user-settings.

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

---------

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

actions/active-sprint.ts

@@ -7,7 +7,7 @@ import { z } from 'zod'
 import { prisma } from '@/lib/prisma'
 import { SessionData, sessionOptions } from '@/lib/session'
 import { productAccessFilter } from '@/lib/product-access'
-import { setActiveSprintCookie } from '@/lib/active-sprint'
+import { setActiveSprintInSettings } from '@/lib/active-sprint'
 
 async function getSession() {
   return getIronSession<SessionData>(await cookies(), sessionOptions)
@@ -36,7 +36,7 @@ export async function setActiveSprintAction(productId: string, sprintId: string)
   })
   if (!sprint) return { error: 'Sprint niet gevonden of niet toegankelijk' }
 
-  await setActiveSprintCookie(parsed.data.productId, parsed.data.sprintId)
+  await setActiveSprintInSettings(session.userId, parsed.data.productId, parsed.data.sprintId)
   revalidatePath('/', 'layout')
   return { success: true, sprintId: parsed.data.sprintId }
 }
@@ -59,5 +59,5 @@ export async function syncActiveSprintCookieAction(productId: string, sprintId:
   })
   if (!sprint) return
 
-  await setActiveSprintCookie(parsed.data.productId, parsed.data.sprintId)
+  await setActiveSprintInSettings(session.userId, parsed.data.productId, parsed.data.sprintId)
 }

actions/sprints.ts

@@ -14,7 +14,7 @@ import {
 import { enforceUserRateLimit } from '@/lib/rate-limit'
 import { propagateStatusUpwards } from '@/lib/tasks-status-update'
 import { createWithCodeRetry, generateNextSprintCode } from '@/lib/code-server'
-import { setActiveSprintCookie } from '@/lib/active-sprint'
+import { setActiveSprintInSettings } from '@/lib/active-sprint'
 import { z } from 'zod'
 
 async function getSession() {
@@ -102,7 +102,7 @@ export async function createSprintAction(_prevState: unknown, formData: FormData
     }
   }
 
-  await setActiveSprintCookie(parsed.data.productId, sprint.id)
+  await setActiveSprintInSettings(session.userId, parsed.data.productId, sprint.id)
   revalidatePath(`/products/${parsed.data.productId}`, 'layout')
   return { success: true, sprintId: sprint.id }
 }
@@ -409,7 +409,7 @@ export async function createSprintWithPbisAction(input: {
       }),
   )
 
-  await setActiveSprintCookie(parsed.data.productId, sprint.id)
+  await setActiveSprintInSettings(session.userId, parsed.data.productId, sprint.id)
   revalidatePath(`/products/${parsed.data.productId}`, 'layout')
   return { success: true, sprintId: sprint.id }
 }