fix(mam, log): improve datetime handling and memory management in MAM and log fetching

- Introduce static helper `_truncate_datetime_suffix()` to safely trim datetime strings, removing unwanted suffixes like timezone offsets
- Replace manual string management with auto_gchar and g_strdup for safer, clearer ownership and to prevent leaks
- Add safety checks and logging warnings for unexpected datetime string lengths or null pointers
- Refactor _mam_rsm_id_handler to use the helper function and updated string handling
- Change log_database_get_previous_chat parameters for consistent ownership semantics, avoiding double frees and mem leaks
- Overall improve stability and prevent memory leaks during log database queries

src/database.c

@@ -320,7 +320,7 @@ log_database_get_limits_info(const gchar* const contact_barejid, gboolean is_las
 // null the current time is used. from_start gets first few messages if true
 // otherwise the last ones. Flip flips the order of the results
 db_history_result_t
-log_database_get_previous_chat(const gchar* const contact_barejid, const char* start_time, char* end_time, gboolean from_start, gboolean flip, GSList** result)
+log_database_get_previous_chat(const gchar* const contact_barejid, const gchar* start_time, const gchar* end_time, gboolean from_start, gboolean flip, GSList** result)
 {
     if (!g_chatlog_database) {
         log_warning("log_database_get_previous_chat() called but db is not initialized");
@@ -337,7 +337,7 @@ log_database_get_previous_chat(const gchar* const contact_barejid, const char* s
     gchar* sort1 = from_start ? "ASC" : "DESC";
     gchar* sort2 = !flip ? "ASC" : "DESC";
     GDateTime* now = g_date_time_new_now_local();
-    auto_gchar gchar* end_date_fmt = end_time ? end_time : g_date_time_format_iso8601(now);
+    auto_gchar gchar* end_date_fmt = end_time ? g_strdup(end_time) : g_date_time_format_iso8601(now);
     auto_sqlite gchar* query = sqlite3_mprintf("SELECT * FROM ("
                                                "SELECT COALESCE(B.`message`, A.`message`) AS message, "
                                                "A.`timestamp`, A.`from_jid`, A.`from_resource`, A.`to_jid`, A.`to_resource`, A.`type`, A.`encryption`, A.`stanza_id` FROM `ChatLogs` AS A "