feat: add CPU and memory resource limits per app

- Add cpu_limit (REAL) and memory_limit (INTEGER) columns to apps table
  via migration 007
- Add CPULimit and MemoryLimit fields to App model with full CRUD support
- Add resource limits fields to app edit form with human-friendly
  memory input (e.g. 256m, 1g, 512k)
- Pass CPU and memory limits to Docker container creation via
  NanoCPUs and Memory host config fields
- Extract Docker container creation helpers (buildEnvSlice, buildMounts,
  buildResources) for cleaner code
- Add formatMemoryBytes template function for display
- Add comprehensive tests for parsing, formatting, model persistence,
  and container options

templates/templates_test.go

@@ -0,0 +1,34 @@
+package templates //nolint:testpackage // tests unexported formatMemoryBytes
+
+import (
+	"testing"
+)
+
+func TestFormatMemoryBytes(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		bytes    int64
+		expected string
+	}{
+		{"gigabytes", 1024 * 1024 * 1024, "1g"},
+		{"two gigabytes", 2 * 1024 * 1024 * 1024, "2g"},
+		{"megabytes", 256 * 1024 * 1024, "256m"},
+		{"kilobytes", 512 * 1024, "512k"},
+		{"plain bytes", 12345, "12345"},
+		{"non-even megabytes", 256*1024*1024 + 1, "268435457"},
+		{"zero", 0, "0"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := formatMemoryBytes(tt.bytes)
+			if got != tt.expected {
+				t.Errorf("formatMemoryBytes(%d) = %q, want %q", tt.bytes, got, tt.expected)
+			}
+		})
+	}
+}