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/core/piinit.h

@@ -32,11 +32,11 @@
 #include "pibase.h"
 
 // PIInit stub: enabled for embedded or when core features are missing
-#if defined(PIP_EMBEDDED) || (defined(PIP_NO_THREADS) && defined(PIP_NO_FILESYSTEM))
+#if defined(PIP_EMBEDDED) || (!defined(PIP_HAS_THREADS) && !defined(PIP_HAS_FILESYSTEM))
 #  define _PIP_INIT_STUB_
 #endif
 
-#ifndef PIP_NO_THREADS
+#ifdef PIP_HAS_THREADS
 
 #  include "piincludes.h"
 
@@ -127,5 +127,5 @@ private:
 };
 
 
-#endif // PIP_NO_THREADS
+#endif // PIP_HAS_THREADS
 #endif // PIINIT_H