Add per-worker stats page with cumulative work and luck

Expose ckpool's per-worker cumulative shares via patch 0004, add a
WorkerDetailPage with hashrate, status, best share with per-worker luck
(bestever/shares*100), and total work with pool share percentage.
Worker names are now clickable in MinersTable and UserDetailPage.
Also centers numeric columns below their headers.

api/internal/ckpool/types.go

@@ -69,6 +69,7 @@ type Worker struct {
 	LastShare int64   `json:"lastshare"`
 	BestDiff  float64 `json:"bestdiff"`
 	BestEver  float64 `json:"bestever"`
+	Shares    int64   `json:"shares"`
 	MinDiff   float64 `json:"mindiff"`
 	Idle      bool    `json:"idle"`
 }