refactor: rename PIP_NO_\* to PIP_HAS_\* with inverted logic

All feature flags now use positive naming (enabled by default):
- PIP_HAS_FILESYSTEM, PIP_HAS_THREADS, PIP_HAS_SOCKET
- PIP_HAS_PROCESS, PIP_HAS_DYNLIB, PIP_HAS_FFT, PIP_HAS_SERIAL

Preprocessor guards inverted:
- #ifndef PIP_NO_X → #ifdef PIP_HAS_X
- #ifdef PIP_NO_X → #ifndef PIP_HAS_X

CMake options default ON instead of OFF.
Platform blocks set flags OFF to disable features.

85 files transformed via Python script + 2 manual fixes.

libs/main/io_devices/pican.cpp

@@ -20,7 +20,7 @@
 
 #include "pipropertystorage.h"
 #include "piwaitevent_p.h"
-#if !defined(WINDOWS) && !defined(MAC_OS) && !defined(PIP_NO_SOCKET)
+#if !defined(WINDOWS) && !defined(MAC_OS) && defined(PIP_HAS_SOCKET)
 #  define PIP_CAN
 #endif
 #ifdef PIP_CAN