fix: CWE-134 format string audit and compiler hardening

Security:
Fix CWE-134 in iq.c: user-controlled string passed as format argument
Add G_GNUC_PRINTF annotations to all variadic printf-like wrappers
in ui.h, log.h and http_common.h
Compiler flags (configure.ac):

Replace basic -Wformat/-Wformat-nonliteral with -Wformat=2
Add -Wextra, -Wnull-dereference, -Wpointer-arith,
-Wimplicit-function-declaration, -Wundef, -Wfloat-equal,
-Wredundant-decls, -Walloc-zero
Add -fstack-protector-strong, -fno-common, -D_FORTIFY_SOURCE=2
Add GCC-specific flags via AC_COMPILE_IFELSE: -Wlogical-op,
-Wduplicated-cond, -Wduplicated-branches, -Wstringop-overflow,
-Warray-bounds=2
Suppress noisy -Wextra sub-warnings: -Wno-unused-parameter,
-Wno-missing-field-initializers, -Wno-sign-compare,
-Wno-cast-function-type
Remove AM_CFLAGS/CFLAGS duplication
Bug fixes found by new warnings:

chatlog.c: non-MUCPM redact path passed resourcepart instead of NULL
rosterwin.c: merge duplicated if/else branches into single condition
omemo.c: redundant else-if in omemo_automatic_start; remove
unnecessary scope block and goto, use early return
console.c: pointer compared to integer 0 instead of NULL
stanza.c: increase pri_str/idle_str buffers from 10 to 12 bytes
(INT_MIN = -2147483648 needs 12 bytes including NUL)
vcard.c: NULL guard for filename before g_file_set_contents
api.c: broken log_warning() calls with extra format argument
Format mismatch fixes:

chatwin.c: Jid* → char* for %s
connection.c: %x → %lx for long flags
cmd_funcs.c: %d → %zu for size_t; cast gpointer to char* for %s
cmd_defs.c: %d → %u for g_list_length() return (guint)
iq.c: barejid → fulljid for from_jid
console.c, mucwin.c, privwin.c, account.c, omemo.c, presence.c:
gpointer → (char*) casts for %s
Const-correctness and cleanup:

database.c: const for type, query, sort variables
form.c/xmpp.h: const for form_set_value parameter
files.c: refactor to early return, eliminating NULL logfile path
muc.c/muc.h: remove meaningless top-level const on return type
common.c: const for URL string literal
Remove stale declarations: cons_show_desktop_prefs (ui.h),
connection_set_priority (connection.h),
omemo_devicelist_configure_and_request (omemo.h)
test_common.c: add currb NULL check to silence -Wnull-dereference
Tooling (check-cwe134.sh):

Reduce from 5 checks to 2 (checks 1-3 redundant with -Wformat=2)
Check 1: verify known wrappers have G_GNUC_PRINTF attribute
Check 2: auto-detect unannotated variadic printf-like functions
Match both const char* and const gchar* in variadic patterns

Author: jabber.developer2 <jabber.developer2@jabber.space>

src/xmpp/omemo.c

@@ -353,6 +353,7 @@ omemo_receive_message(xmpp_stanza_t* const stanza, gboolean* trusted)
 {
     char* plaintext = NULL;
     const char* type = xmpp_stanza_get_type(stanza);
+    const char* from = xmpp_stanza_get_from(stanza);
     GList* keys = NULL;
     unsigned char* iv_raw = NULL;
     unsigned char* payload_raw = NULL;
@@ -434,8 +435,6 @@ omemo_receive_message(xmpp_stanza_t* const stanza, gboolean* trusted)
         keys = g_list_append(keys, key);
     }
 
-    const char* from = xmpp_stanza_get_from(stanza);
-
     plaintext = omemo_on_message_recv(from, sid, iv_raw, iv_len,
                                       keys, payload_raw, payload_len,
                                       g_strcmp0(type, STANZA_TYPE_GROUPCHAT) == 0, trusted);
@@ -471,7 +470,8 @@ _omemo_receive_devicelist(xmpp_stanza_t* const stanza, void* const userdata)
 
         const char* code = xmpp_stanza_get_attribute(error, "code");
         if (g_strcmp0(code, "404") == 0) {
-            goto out;
+            omemo_set_device_list(from, NULL);
+            return 1;
         }
     }
 
@@ -517,7 +517,8 @@ _omemo_receive_devicelist(xmpp_stanza_t* const stanza, void* const userdata)
         log_warning("[OMEMO] User %s has a non 'current' device item list: %s.", from, xmpp_stanza_get_id(first));
         item = first;
     } else {
-        goto out;
+        omemo_set_device_list(from, device_list);
+        return 1;
     }
 
     xmpp_stanza_t* list = xmpp_stanza_get_child_by_ns(item, STANZA_NS_OMEMO);
@@ -539,7 +540,6 @@ _omemo_receive_devicelist(xmpp_stanza_t* const stanza, void* const userdata)
         }
     }
 
-out:
     omemo_set_device_list(from, device_list);
 
     return 1;