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/templates/style.css

@@ -840,6 +840,27 @@ select.form-control option { background: var(--bg-secondary); color: var(--text-
     background: rgba(35, 134, 54, 0.45);
     border: 1px solid #4edf72;
 }
+.memory-dist-bar {
+    width: 100%;
+    height: 14px;
+    border-radius: 7px;
+    display: flex;
+    overflow: hidden;
+    background: var(--bg-secondary);
+    border: 1px solid var(--border-color);
+}
+.memory-dist-bar .memory-bar-segment:first-child {
+    border-radius: 6px 0 0 6px;
+}
+.memory-dist-bar .memory-bar-segment:last-child {
+    border-radius: 0 6px 6px 0;
+}
+.memory-dist-header {
+    font-size: .85rem;
+    color: var(--text-secondary);
+    margin-bottom: .5rem;
+    font-family: 'JetBrains Mono', monospace;
+}
 
 /* Logs */
 .logs-container {