feat(#233): timeline UX rework

[NickMonrad]

Summary

Reworks the timeline experience and related optimiser flows, including new planning drawers, scheduling logic, and supporting timeline/resource UI updates.

Related issue

Closes #233

Changes

• Rework timeline/Gantt UX and supporting client-side planning flows
• Add optimiser and scheduler backend/frontend changes used by the new timeline workflows
• Stabilise planner demand allocation, named-resource assignment visibility, and resource profile exports
• Address PR review fixes and align Playwright coverage with the renamed Timeline UX

E2E Tests

Tests added/modified:

• e2e/tests/timeline.spec.ts - updated Timeline and Starting Team Finder selectors/copy for the current UX
• e2e/tests/gantt.spec.ts - updated Quick schedule flow selectors
• e2e/tests/helpers.ts - added shared quickSchedule() and openStartingTeamFinder() helpers
• e2e/TESTS.md - updated test inventory/documentation for the renamed Timeline UX

E2E test results (npm run test:e2e):

Targeted local rerun of the affected Timeline/Gantt specs was partially blocked by local auth rate limiting.
PR CI rerun is the source of truth for this selector update.

Testing

• npm test passes in /server
• npx tsc --noEmit passes in /server
• npx tsc --noEmit passes in /client
• npm run test:e2e passes (Playwright - requires dev servers on :3001 and :5173)
• e2e/TESTS.md updated to reflect any test additions or changes

Manual testing

• Expired session recovery: log in, expire or clear the token, refresh, and confirm the app returns cleanly to Login instead of getting stuck in 401/reload loops.
• Reset password: complete the reset flow, then immediately log in with the new password and confirm rate limiting does not block the first successful login.
• Timeline named-resource histogram: open the affected timeline and confirm named resources now show allocation beyond week 1 and match the visible demand span.
• Timeline -> Resource Profile / Commercial sync: change allocation mode, counts, or named-resource settings on Timeline, then navigate straight to Resource Profile and Commercial and confirm the new values appear without stale data.
• Resource Profile allocation consistency: for roles such as Senior Engineer - Data, AI & IoT, confirm row-level allocated days and timing agree with the per-person actual allocation and histogram coverage.
• Parallel warning edge case: recheck the project that previously showed 19.5 needed, 19.5 available and confirm that false-positive warning is gone, while a real over-capacity case still warns.
• Capacity-plan exit: switch a resource type out of CAPACITY_PLAN into manual/timeline-style editing and confirm both the resource type and its named resources transition consistently with no mixed-mode leftovers.

Notes

• Review findings were addressed in follow-up commits on this branch.
• Latest CI-triggering fix updates Playwright selectors to the current Timeline wording: Quick schedule and Starting Team Finder.

[NickMonrad]

Review findings ordered by fix priority:

1. P1 — cross-project resource mutation in optimiser apply
   server/src/routes/optimiser.ts:147-163 updates resourceType by bare { id: rtId } and namedResource.updateMany({ where: { resourceTypeId: rtId } }) after only checking ownedProject(projectId) for the URL project. Because ResourceType / NamedResource IDs are global rather than project-scoped (server/prisma/schema.prisma:91-113, 347-363), a user who knows another project's resource type ID can mutate that other project's counts/start weeks.

2. P1 — dependency arrows are painted underneath the chart background
   client/src/components/timeline/GanttChart.tsx:351-366 renders dependency arrows before the opaque background <rect>, so SVG paint order hides them entirely. On main, the arrows render after the background.

3. P1 — Team Finder settings reset while the drawer is open
   client/src/components/timeline/TimelineOptimiserDrawer.tsx:353-380 makes resetSettings depend on resourceTypes, and the open-state effect depends on resetSettings. client/src/pages/TimelinePage.tsx:467-472 passes a fresh mapped resourceTypes array every render, so parent re-renders while open reset in-progress Team Finder settings.

4. P1 — Squad Planner edits are overwritten while the drawer is open
   client/src/components/timeline/SquadPlannerDrawer.tsx:217-247 has the same unstable resourceTypes dependency problem. Re-renders retrigger the restore effect and can reload localStorage over unsaved in-progress edits.

5. P2 — invalid count ranges can produce divide-by-zero scheduling output
   server/src/routes/optimiser.ts:327-333 accepts caller-supplied countRanges without enforcing min >= 1. server/src/lib/scheduler.ts:420-421 then divides by count, so min: 0 can propagate Infinity / NaN through scenario scoring.

6. P2 — over-allocation dot becomes stale while dragging
   client/src/components/timeline/GanttBar.tsx:111-117,135-137 determines dot visibility from committed entry.startWeek but positions it from live effectiveStart. During drag, the indicator can show the wrong state.

7. P2 — named-resource bars can overflow the chart with onboarding weeks
   client/src/pages/TimelinePage.tsx:108,182-199 defaults named-resource endWeek to totalWeeks - 1, then bar positioning also adds weekOffset. With onboarding weeks and no explicit end week, the bar extends past the chart width.

8. P3 — duplicate epic-dependency query in schedule route
   server/src/routes/timeline.ts:478-481 and 549-552 fetch the same dependency set twice in one request. Low risk, but wasted DB work on every schedule call.