fix(uptime): replace 'uptime -p' with /proc/uptime parsing

On NixOS, the default `uptime` command from coreutils does not support
the `-p` option.
This replaces the previous `bash`-based solution with a call to
`/proc/uptime`,
and parses the result in JavaScript to produce a human-readable format
like:

    "up 1 day, 2 hours, 5 minutes"

This makes uptime reporting fully compatible with NixOS and more
portable.

Services/UserInfoService.qml

@@ -66,20 +66,35 @@ Singleton {
     Process {
         id: uptimeProcess
 
-        command: ["bash", "-c", "uptime -p | sed 's/up //'"]
+        command: ["cat", "/proc/uptime"]
         running: false
+
         onExited: (exitCode) => {
             if (exitCode !== 0) {
-                
                 root.uptime = "Unknown";
             }
         }
 
         stdout: StdioCollector {
             onStreamFinished: {
-                root.uptime = text.trim() || "Unknown";
-            }
-        }
+                const seconds = parseInt(text.split(" ")[0]);
+                const days = Math.floor(seconds / 86400);
+                const hours = Math.floor((seconds % 86400) / 3600);
+                const minutes = Math.floor((seconds % 3600) / 60);
 
+                const parts = [];
+                if (days > 0)
+                    parts.push(`${days} day${days === 1 ? "" : "s"}`);
+                if (hours > 0)
+                    parts.push(`${hours} hour${hours === 1 ? "" : "s"}`);
+                if (minutes > 0)
+                    parts.push(`${minutes} minute${minutes === 1 ? "" : "s"}`);
+
+                if (parts.length > 0)
+                    root.uptime = "up " + parts.join(", ");
+                else
+                    root.uptime = `up ${seconds} seconds`;
+            }
+        }
     }
 }