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/ui/ui.h

@@ -146,7 +146,7 @@ void chatwin_set_incoming_char(ProfChatWin* chatwin, const char* const ch);
 void chatwin_unset_incoming_char(ProfChatWin* chatwin);
 void chatwin_set_outgoing_char(ProfChatWin* chatwin, const char* const ch);
 void chatwin_unset_outgoing_char(ProfChatWin* chatwin);
-db_history_result_t chatwin_db_history(ProfChatWin* chatwin, const char* start_time, char* end_time, gboolean flip);
+db_history_result_t chatwin_db_history(ProfChatWin* chatwin, const gchar* start_time, const gchar* end_time, gboolean flip);
 
 // MUC window
 ProfMucWin* mucwin_new(const char* const barejid);