Phase 5b slice B. dashboardCache deleted. The Server's dashboard field
is now `*cache.TTLCache[*dashboardPayload]` constructed via
`cache.NewTTL[*dashboardPayload](dashboardCacheTTL)`. All call sites
renamed:
- s.dashboard.get(k) → s.dashboard.Get(k)
- s.dashboard.set(k, p) → s.dashboard.Set(k, p)
- s.dashboard.invalidate(k) → s.dashboard.Invalidate(k)
- s.dashboard.invalidateAll → s.dashboard.InvalidateAll
(across web/dashboard.go, web/server.go, web/caldav.go,
web/links.go, web/gitea_writeback.go)
The 64-line dashboardCache struct + methods are gone; the dashboard
file shrinks by ~63 lines. TTL constant lifted out to
`dashboardCacheTTL = 60 * time.Second` so the const lives next to its
semantics rather than a magic-number literal in New().
All web/dashboard_*test.go pass unmodified.
Task: t-projax-5b-cache
mAi
085e672dd5