Persistencia setters, compat-resolved, journald→CAS, compat-polkit

- hostnamed: SetHostname llama sethostname(2) + cache. SetStaticHostname
  escribe atómico a /etc/hostname (tmp + fsync + rename, perms 0644).
  Set{Pretty,Icon,Chassis,Deployment,Location} mergean k=v en
  /etc/machine-info preservando otras keys. Validación: hostname RFC 1123
  + chassis enum.
- timedated: SetTimezone valida que /usr/share/zoneinfo/<tz> exista,
  hace symlink atómico a /etc/localtime.
- localed: SetLocale valida formato KEY=value, escribe a /etc/locale.conf.
- compat-resolved (nuevo): org.freedesktop.resolve1.Manager con
  ResolveHostname (vía tokio::lookup_host) y ResolveAddress (getnameinfo).
  ResolveRecord devuelve NotSupported.
- journald-compat: persiste cada datagram al CAS por SHA. Append a
  ~/.local/share/ente/journal/index.log con
  timestamp_ms:source:unit:sha_hex. Mutex serializa escrituras.
- compat-polkit (nuevo): org.freedesktop.PolicyKit1.Authority always-yes.
  CheckAuthorization/CheckAuthorizationByAsync responden true,false,{}.
  EnumerateActions vacío. Loguea action_id + pid/uid del subject.

7 compat-shims operativos en paralelo.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/ente-localed-compat/src/main.rs

@@ -96,8 +96,21 @@ impl LocaleManager {
     }
 
     async fn set_locale(&self, locale: Vec<String>, _interactive: bool) -> fdo::Result<()> {
-        info!(?locale, "SetLocale (stub: no persistimos a /etc/locale.conf)");
-        *self.transient_locale.lock().unwrap() = Some(locale);
+        // Validar formato KEY=value en cada entry.
+        for entry in &locale {
+            if !entry.contains('=') {
+                return Err(fdo::Error::InvalidArgs(
+                    format!("locale entry inválido (sin '='): {entry}")
+                ));
+            }
+        }
+        let content: String = locale.iter()
+            .map(|s| format!("{s}\n"))
+            .collect();
+        atomic_write("/etc/locale.conf", content.as_bytes())
+            .map_err(|e| fdo::Error::Failed(format!("write /etc/locale.conf: {e}")))?;
+        *self.transient_locale.lock().unwrap() = Some(locale.clone());
+        info!(?locale, "SetLocale → /etc/locale.conf");
         Ok(())
     }
 
@@ -126,6 +139,24 @@ impl LocaleManager {
     }
 }
 
+fn atomic_write(path: &str, content: &[u8]) -> std::io::Result<()> {
+    use std::io::Write;
+    use std::os::unix::fs::OpenOptionsExt;
+    let p = std::path::Path::new(path);
+    if let Some(parent) = p.parent() { let _ = std::fs::create_dir_all(parent); }
+    let tmp = p.with_extension("tmp");
+    {
+        let mut f = std::fs::OpenOptions::new()
+            .create(true).write(true).truncate(true)
+            .mode(0o644)
+            .open(&tmp)?;
+        f.write_all(content)?;
+        f.sync_all()?;
+    }
+    std::fs::rename(&tmp, p)?;
+    Ok(())
+}
+
 fn read_kv(path: &str, key: &str) -> Option<String> {
     let content = std::fs::read_to_string(path).ok()?;
     for line in content.lines() {