refactor: single now_unix in hive_sh4re::wire_time

replaces 15 per-module copies (now_unix/now_secs) across hive-c0re and
hive-ag3nt; wire_time already owns the epoch-seconds convention

hive-c0re/src/broker.rs

@@ -4,7 +4,6 @@
 use std::collections::{HashMap, HashSet};
 use std::path::Path;
 use std::sync::Mutex;
-use std::time::{SystemTime, UNIX_EPOCH};
 
 use anyhow::{Context, Result};
 
@@ -13,6 +12,7 @@ use hive_sh4re::{InboxRow, Message};
 use rusqlite::{Connection, OptionalExtension, params};
 use serde::Serialize;
 use tokio::sync::broadcast;
+use hive_sh4re::wire_time::now_unix;
 
 const SCHEMA: &str = r"
 CREATE TABLE IF NOT EXISTS messages (
@@ -1136,13 +1136,6 @@ fn ensure_reminder_columns(conn: &Connection) -> Result<()> {
     )
 }
 
-fn now_unix() -> i64 {
-    SystemTime::now()
-        .duration_since(UNIX_EPOCH)
-        .ok()
-        .and_then(|d| i64::try_from(d.as_secs()).ok())
-        .unwrap_or(0)
-}
 
 #[cfg(test)]
 mod tests {