containers: Docker (and best-effort Podman) plugin

- minimal Docker Engine API client over Unix/TCP sockets with version
  negotiation and chunked response decoding
- drop-in stats schema: active/stopped containers, CPU/memory/IO/network
  rates, ports, uptime (pretty_date), image, engine field
- Docker + Podman engines, config (all, podman_sock, max_name_size,
  disable_stats, show/hide, per-container thresholds)
- export strips the computation sub-dicts (--stdout/--stdout-csv)
- TUI block above the process count
- CI-safe fake Docker socket test + live differential parity

crates/glances-core/src/units.rs

@@ -115,6 +115,64 @@ pub fn bar_custom(
     bar
 }
 
+/// Get a datetime or a timestamp and return a pretty string like
+/// 'an hour ago', 'yesterday', '3 months ago', 'just now'...
+/// (port of `glances.globals.pretty_date`).
+pub fn pretty_date(
+    started: chrono::DateTime<chrono::Local>,
+    now: chrono::DateTime<chrono::Local>,
+) -> String {
+    let diff = now.signed_duration_since(started);
+    let day_diff = diff.num_days();
+    if day_diff < 0 {
+        return String::new();
+    }
+    // Python's timedelta.seconds excludes the days.
+    let second_diff = diff.num_seconds() - day_diff * 86_400;
+
+    if day_diff == 0 {
+        let thresholds: [(i64, i64, Option<&str>, Option<&str>); 6] = [
+            (10, 1, Some("just now"), None),
+            (60, 1, None, Some(" secs")),
+            (120, 1, Some("a min"), None),
+            (3600, 60, None, Some(" mins")),
+            (7200, 1, Some("an hour"), None),
+            (86_400, 3600, None, Some(" hours")),
+        ];
+        for (max_value, divisor, singular, plural) in thresholds {
+            if second_diff < max_value {
+                if let Some(singular) = singular
+                    && plural.is_none()
+                {
+                    return singular.to_string();
+                }
+                let value = second_diff / divisor;
+                return format!("{value}{}", plural.unwrap_or(""));
+            }
+        }
+    }
+
+    let day_thresholds: [(i64, i64, Option<&str>, Option<&str>); 5] = [
+        (2, 1, Some("yesterday"), None),
+        (7, 1, Some("a day"), Some(" days")),
+        (31, 7, Some("a week"), Some(" weeks")),
+        (365, 30, Some("a month"), Some(" months")),
+        (i64::MAX, 365, Some("an year"), Some(" years")),
+    ];
+    for (max_days, divisor, singular, plural) in day_thresholds {
+        if day_diff < max_days {
+            let value = day_diff / divisor;
+            if let Some(singular) = singular
+                && (value <= 1 || plural.is_none())
+            {
+                return singular.to_string();
+            }
+            return format!("{value}{}", plural.unwrap_or(""));
+        }
+    }
+    String::new()
+}
+
 /// Parse a value like `'12.5 MB'` into a float (port of `string_value_to_float`).
 pub fn string_value_to_float(s: &str) -> Option<f64> {
     let cleaned: String = s.chars().filter(|c| *c != ' ').collect();