v0.27.3: Use real system memory everywhere, add monitoring memory bar

Deploy page, pre-start check, and deploy validation now use actual
/proc/meminfo usage instead of declared mem_request sums. New
GetMemoryMB() helper for lightweight real-time memory reads. Monitoring
page gains a stacked memory distribution bar showing per-container
usage, OS overhead, and free memory.

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

controller/internal/web/handlers.go

@@ -354,35 +354,36 @@ func (s *Server) deployHandler(w http.ResponseWriter, r *http.Request, name stri
 	// Memory info for deploy page (only for non-deployed apps)
 	if !alreadyDeployed {
 		memInfo := map[string]interface{}{"Available": false}
-		totalMB, memErr := system.GetTotalMemoryMB()
+		totalMB, usedMB, memErr := system.GetMemoryMB()
 		if memErr == nil {
 			reservedMB := s.cfg.System.ReservedMemoryMB
 			usableMB := totalMB - reservedMB
-			committedReqMB, committedLimitMB := s.stackMgr.CommittedMemory()
 			newReqMB := stacks.ParseMemoryMB(meta.Resources.MemRequest)
-			newLimitMB := stacks.ParseMemoryMB(meta.Resources.MemLimit)
-			afterReqMB := committedReqMB + newReqMB
-			afterLimitMB := committedLimitMB + newLimitMB
+			afterMB := usedMB + newReqMB
 			percent := 0
 			if usableMB > 0 {
-				percent = afterReqMB * 100 / usableMB
+				percent = afterMB * 100 / usableMB
+			}
+			usedPercent := 0
+			if usableMB > 0 {
+				usedPercent = usedMB * 100 / usableMB
 			}
 
-			committedPercent := 0
-			if usableMB > 0 {
-				committedPercent = committedReqMB * 100 / usableMB
-			}
+			// Overcommit warning still uses declared limits
+			_, committedLimitMB := s.stackMgr.CommittedMemory()
+			newLimitMB := stacks.ParseMemoryMB(meta.Resources.MemLimit)
+			afterLimitMB := committedLimitMB + newLimitMB
 
 			memInfo["Available"] = true
 			memInfo["TotalMB"] = totalMB
 			memInfo["ReservedMB"] = reservedMB
 			memInfo["UsableMB"] = usableMB
-			memInfo["CommittedMB"] = committedReqMB
+			memInfo["UsedMB"] = usedMB
 			memInfo["NewRequestMB"] = newReqMB
-			memInfo["AfterMB"] = afterReqMB
+			memInfo["AfterMB"] = afterMB
 			memInfo["Percent"] = percent
-			memInfo["CommittedPercent"] = committedPercent
-			memInfo["Blocked"] = newReqMB > 0 && afterReqMB > usableMB
+			memInfo["UsedPercent"] = usedPercent
+			memInfo["Blocked"] = newReqMB > 0 && afterMB > usableMB
 			memInfo["OvercommitWarn"] = newLimitMB > 0 && afterLimitMB > totalMB
 		}
 		data["MemoryInfo"] = memInfo