fix: CWE-134 format string vulnerability audit

Security:
- Fix CWE-134 in iq.c: user-controlled string passed as format arg

Annotations:
- Add G_GNUC_PRINTF to variadic functions in ui.h and log.h

Compiler flags (configure.ac):
- Add -Wformat -Wformat-nonliteral -Wno-format-zero-length

Format mismatch fixes:
- chatwin.c: Jid* instead of char* for %s
- connection.c: %x -> %lx for long flags
- cmd_funcs.c: %d -> %zu for MB_CUR_MAX/MB_LEN_MAX (size_t)
- cmd_funcs.c: cast gpointer to (char*) for %s
- cmd_defs.c: %d -> %u for g_list_length() (guint)
- iq.c: from_jid->barejid -> from_jid->fulljid
- console.c, mucwin.c, privwin.c, account.c, omemo.c, presence.c:
  gpointer -> (char*) casts for %s

Bug fixes:
- api.c: broken log_warning() calls with extra format arg
- cmd_funcs.c: remove unused arg from cons_show()

Tooling:
- Expand check-cwe134.sh detection patterns

configure.ac

@@ -385,7 +385,7 @@ AC_CHECK_LIB([util], [forkpty], [AM_CONDITIONAL([HAVE_FORKPTY], [true]) FORKPTY_
 AC_SUBST([FORKPTY_LIB])
 
 ## Default parameters
-AM_CFLAGS="$AM_CFLAGS -Wall -Wno-deprecated-declarations -std=gnu99 -ggdb3"
+AM_CFLAGS="$AM_CFLAGS -Wall -Wformat -Wformat-nonliteral -Wno-format-zero-length -Wno-deprecated-declarations -std=gnu99 -ggdb3"
 AM_LDFLAGS="$AM_LDFLAGS -export-dynamic"
 
 AS_IF([test "x$enable_coverage" = xyes],