feat: GPU process list with per-process VRAM/utilization and kill

Add a GPU process table to the Performance tab showing which processes
use the selected GPU, with per-process VRAM, GPU utilization, CPU, host
memory, and command. Includes a kill endpoint (SIGTERM/SIGKILL, with
optional parent kill) behind a confirm dialog.

- nvcurve/hal/processes.py: NVML + /proc process enumeration
- server.py: GET /api/processes, POST /api/processes/kill (refuses to
  signal init/kthreadd)
- frontend: ProcessList component, API client, types
- tests: test_processes.py
- docs: API reference for the new endpoints

frontend/src/App.tsx

@@ -9,6 +9,7 @@ import { CurveEditor } from "./components/CurveEditor/CurveEditor.js";
 import { PointTable } from "./components/PointTable/PointTable.js";
 import { PerformancePanel } from "./components/Limits/PerformancePanel.js";
 import { PerformanceMonitor } from "./components/Monitor/PerformanceMonitor.js";
+import { ProcessList } from "./components/Monitor/ProcessList.js";
 import { FanMonitor } from "./components/Monitor/FanMonitor.js";
 import { FanCurveEditor } from "./components/Fans/FanCurveEditor.js";
 import { WireViewPanel } from "./components/WireView/WireViewPanel.js";
@@ -290,16 +291,19 @@ function MainApp({
               )}
             </>
           ) : activeTab === "performance" ? (
-            <div className="flex gap-4 items-start w-full">
-              <div className="flex-1 min-w-0">
-                <PerformancePanel />
-              </div>
-              <div className="w-80 shrink-0 flex flex-col">
-                <PerformanceMonitor
-                  monitor={monitor}
-                  history={monitorHistory}
-                />
+            <div className="flex flex-col gap-4 w-full">
+              <div className="flex gap-4 items-start w-full">
+                <div className="flex-1 min-w-0">
+                  <PerformancePanel />
+                </div>
+                <div className="w-80 shrink-0 flex flex-col">
+                  <PerformanceMonitor
+                    monitor={monitor}
+                    history={monitorHistory}
+                  />
+                </div>
               </div>
+              <ProcessList />
             </div>
           ) : activeTab === "wireview" ? (
             <WireViewPanel