fix timestamp format for AT Protocol compatibility

Use ISO 8601 with milliseconds and Z suffix instead of rfc3339 with nanoseconds and +00:00 offset.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main.rs

@@ -326,6 +326,11 @@ fn new_id() -> String {
     Uuid::new_v4().to_string().replace('-', "")[..13].to_string()
 }
 
+/// ISO 8601 format compatible with AT Protocol: "2026-03-22T07:21:00.448Z"
+fn now_iso() -> String {
+    Utc::now().format("%Y-%m-%dT%H:%M:%S%.3fZ").to_string()
+}
+
 // --- DB ---
 
 fn init_db(conn: &Connection) {
@@ -395,7 +400,7 @@ fn init_db(conn: &Connection) {
 fn ensure_account(conn: &Connection, did: &str) {
     conn.execute(
         "INSERT OR IGNORE INTO accounts (did, handle, created_at) VALUES (?1, ?2, ?3)",
-        rusqlite::params![did, did, Utc::now().to_rfc3339()],
+        rusqlite::params![did, did, now_iso()],
     )
     .ok();
 }
@@ -432,7 +437,7 @@ fn get_or_create_convo(conn: &Connection, members: &[String]) -> ConvoView {
     // Create new convo
     let id = new_id();
     let rev = new_rev();
-    let now = Utc::now().to_rfc3339();
+    let now = now_iso();
 
     conn.execute(
         "INSERT INTO convos (id, rev, created_at, updated_at) VALUES (?1, ?2, ?3, ?4)",
@@ -459,7 +464,7 @@ fn get_or_create_convo(conn: &Connection, members: &[String]) -> ConvoView {
 }
 
 fn add_log(conn: &Connection, convo_id: &str, rev: &str, log_type: &str, data: serde_json::Value) {
-    let now = Utc::now().to_rfc3339();
+    let now = now_iso();
     conn.execute(
         "INSERT INTO logs (convo_id, rev, log_type, data, created_at) VALUES (?1, ?2, ?3, ?4, ?5)",
         rusqlite::params![convo_id, rev, log_type, data.to_string(), now],
@@ -583,7 +588,7 @@ fn build_message_json(row: &rusqlite::Row) -> rusqlite::Result<serde_json::Value
 fn insert_message(conn: &Connection, convo_id: &str, did: &str, msg: &MessageInput) -> (String, String, String) {
     let msg_id = new_id();
     let rev = new_rev();
-    let now = Utc::now().to_rfc3339();
+    let now = now_iso();
     let facets_str = msg.facets.as_ref().map(|v| v.to_string());
     let embed_str = msg.embed.as_ref().map(|v| v.to_string());
 
@@ -966,7 +971,7 @@ async fn delete_message_for_self(
     let did = require_auth(&headers)?;
     let db = state.db.lock().unwrap();
     let rev = new_rev();
-    let now = Utc::now().to_rfc3339();
+    let now = now_iso();
 
     db.execute(
         "UPDATE messages SET deleted = 1, rev = ?1 WHERE id = ?2 AND convo_id = ?3",
@@ -1020,7 +1025,7 @@ async fn add_reaction(
 ) -> Result<Json<serde_json::Value>, (StatusCode, Json<ErrorResp>)> {
     let did = require_auth(&headers)?;
     let db = state.db.lock().unwrap();
-    let now = Utc::now().to_rfc3339();
+    let now = now_iso();
     let rev = new_rev();
 
     db.execute(