feat(storage): paginate operations history with prev/next controls

Backend:
- ListStorageJobs(limit, offset) adds OFFSET for pagination
- CountStorageJobs() returns total row count for UI
- handler returns { jobs, total, limit, offset }
- JobManager.List(limit, offset) updated signature

Frontend:
- loadJobs(offset) with default 0
- Pagination UI: 'Mostrando X-Y de Z' + Anterior/Siguiente buttons
- After job start/end, reloads from offset 0
- listStorageJobs(limit, offset) API updated

Tests: fix List/ListStorageJobs calls to include offset=0

Makefile

@@ -1,5 +1,5 @@
 BINARY=nasctl
-VERSION?=0.8.2
+VERSION?=0.8.3
 GO?=go
 LDFLAGS=-s -w -X github.com/darroyo/nasctl/internal/web.Version=$(VERSION) -X github.com/darroyo/nasctl/internal/web.Commit=$(shell git rev-parse --short HEAD 2>/dev/null || echo unknown)
 BUILD_FLAGS=CGO_ENABLED=0