ci: improve CI stability with parallel builds and Valgrind

Major changes:
Run 4 build configurations in parallel with Valgrind on Linux
Add test failure detection verification (meta-test)
Port allocation per build to prevent conflicts in parallel runs
Add --coverage-only flag for dedicated coverage builds
Code quality:

Add TEST_GROUPS constant, CMOCKA patterns, helper functions
Organize ci-build.sh into sections

tests/functionaltests/functionaltests.c

@@ -69,6 +69,12 @@ main(int argc, char* argv[])
         }
     }
 
+    char group_env[16];
+    snprintf(group_env, sizeof(group_env), "%d", group);
+    setenv("PROF_TEST_GROUP", group_env, 1);
+    
+    fprintf(stderr, "[PROF_TEST] Starting functional tests, group=%d\n", group);
+
     /* ============================================================
      * GROUP 1: Connect, Ping, Rooms, Software
      * Basic XMPP session establishment and server queries