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_utils/pidiagnostics.h

@@ -29,7 +29,7 @@
 #include "pitimer.h"
 
 
-#ifndef PIP_NO_THREADS
+#ifdef PIP_HAS_THREADS
 //! \~\ingroup IO-Utils
 //! \brief
 //! \~english Connection diagnostics for packet frequency, throughput and receive quality
@@ -236,6 +236,6 @@ inline bool operator!=(const PIDiagnostics::Entry & f, const PIDiagnostics::Entr
 inline bool operator<(const PIDiagnostics::Entry & f, const PIDiagnostics::Entry & s) {
 	return f.bytes_ok < s.bytes_ok;
 }
-#endif // PIP_NO_THREADS
+#endif // PIP_HAS_THREADS
 
 #endif // PIDIAGNOSTICS_H