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>

CHANGELOG.md

@@ -1,5 +1,15 @@
 ## Changelog
 
+### v0.27.3 — Real System Memory Everywhere (2026-02-23)
+
+#### Changed
+- **Deploy page uses real system memory** — Memory bar now shows actual `/proc/meminfo` usage instead of declared `mem_request` sums. Labels changed from "Jelenlegi foglalás" to "Jelenlegi használat". `system.GetMemoryMB()` provides real-time total and used memory.
+- **Pre-start memory check uses real memory** — `actionStack("start")` in `router.go` and `DeployStack()` in `deploy.go` now check real used memory (`usedMB + newReqMB > usableMB`) instead of declared committed sums. `CommittedMemory()` kept only for soft overcommit warnings.
+
+#### Added
+- **`system.GetMemoryMB()` helper** — Lightweight function in `internal/system/info_linux.go` that returns real total and used memory from `/proc/meminfo` without the overhead of full `GetInfo()` (no disk/CPU/temp). Stub in `info_other.go` for non-Linux.
+- **Monitoring page memory distribution bar** — New stacked bar on `/monitoring` showing per-container memory usage (colored segments), OS/system overhead (gray), and free memory. Built dynamically from container summary data + real-time `/api/system/info`. Color-coded legend with per-app labels.
+
 ### v0.27.2 — Comprehensive Fixes and New Labels (2026-02-23)
 
 #### Fixed