fix(webui): prevent orphaned workers on restart, reduce metrics polling, add Kill Workers button

- tasks: mark TaskRunning tasks as TaskFailed on bee-web restart instead of
  re-queueing them — prevents duplicate gpu-burn-worker spawns when bee-web
  crashes mid-test (each restart was launching a new set of 8 workers on top
  of still-alive orphans from the previous crash)
- server: reduce metrics collector interval 1s→5s, grow ring buffer to 360
  samples (30 min); cuts nvidia-smi/ipmitool/sensors subprocess rate by 5×
- platform: add KillTestWorkers() — scans /proc and SIGKILLs bee-gpu-burn,
  stress-ng, stressapptest, memtester without relying on pkill/killall
- webui: add "Kill Workers" button next to Cancel All; calls
  POST /api/tasks/kill-workers which cancels the task queue then kills
  orphaned OS-level processes; shows toast with killed count
- metricsdb: sort GPU indices and fan/temp names after map iteration to fix
  non-deterministic sample reconstruction order (flaky test)
- server: fix chartYAxisNumber to use one decimal place for 1000–9999
  (e.g. "1,7к" instead of "2к") so Y-axis ticks are distinguishable

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/metricsdb.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sort"
 	"strconv"
 	"time"
 
@@ -217,7 +218,9 @@ func (m *MetricsDB) loadSamples(query string, args ...any) ([]platform.LiveMetri
 		}
 	}
 
-	// Collect unique GPU indices and fan names from loaded data (preserve order)
+	// Collect unique GPU indices and fan/temp names from loaded data.
+	// Sort each list so that sample reconstruction is deterministic regardless
+	// of Go's non-deterministic map iteration order.
 	seenGPU := map[int]bool{}
 	var gpuIndices []int
 	for k := range gpuData {
@@ -226,6 +229,8 @@ func (m *MetricsDB) loadSamples(query string, args ...any) ([]platform.LiveMetri
 			gpuIndices = append(gpuIndices, k.idx)
 		}
 	}
+	sort.Ints(gpuIndices)
+
 	seenFan := map[string]bool{}
 	var fanNames []string
 	for k := range fanData {
@@ -234,6 +239,8 @@ func (m *MetricsDB) loadSamples(query string, args ...any) ([]platform.LiveMetri
 			fanNames = append(fanNames, k.name)
 		}
 	}
+	sort.Strings(fanNames)
+
 	seenTemp := map[string]bool{}
 	var tempNames []string
 	for k := range tempData {
@@ -242,6 +249,7 @@ func (m *MetricsDB) loadSamples(query string, args ...any) ([]platform.LiveMetri
 			tempNames = append(tempNames, k.name)
 		}
 	}
+	sort.Strings(tempNames)
 
 	samples := make([]platform.LiveMetricSample, len(sysRows))
 	for i, r := range sysRows {