refactor: migrate MICRO_PIP to fine-grained feature flags

Replace monolithic MICRO_PIP/PIP_MICRO with granular flags:

Feature flags (CMake options + platform auto-detection):
- PIP_NO_FILESYSTEM, PIP_NO_THREADS, PIP_NO_SOCKET
- PIP_NO_PROCESS, PIP_NO_DYNLIB, PIP_NO_FFT, PIP_NO_SERIAL

Embedded optimization flag:
- PIP_EMBEDDED (auto-set for Pico SDK and FreeRTOS)
  Controls buffer sizes, time stubs, terminal fallback, init stubs

Platform blocks in CMakeLists.txt:
- Pico SDK: auto-disables FS, PROCESS, DYNLIB, FFT, SERIAL;
  conditionally disables THREADS (no FreeRTOS) and SOCKET (no LWIP)
- FreeRTOS: auto-disables FS, PROCESS, DYNLIB, FFT, SERIAL;
  conditionally disables SOCKET (no LWIP)
- Android: auto-disables PROCESS, DYNLIB, FFT

Updated 96 files across libs/, utils/, tests/, and CMakeLists.txt.
Builds verified for Linux (547 tests pass) and Pico SDK (100%).
Removed all MICRO_PIP and PIP_MICRO references (0 remaining).

libs/main/core/piinit.h

@@ -31,6 +31,11 @@
 
 #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))
+#  define _PIP_INIT_STUB_
+#endif
+
 #ifndef PIP_NO_THREADS
 
 #  include "piincludes.h"
@@ -50,11 +55,11 @@ public:
 
 static __PIInit_Initializer__ __piinit_initializer__;
 
-#ifdef MICRO_PIP
-#ifndef PIINIT_MICRO_STUB_DEFINED
-#define PIINIT_MICRO_STUB_DEFINED
+#  ifdef _PIP_INIT_STUB_
+#	ifndef PIINIT_MICRO_STUB_DEFINED
+#	  define PIINIT_MICRO_STUB_DEFINED
 
-int __PIInit_Initializer__::count_ = 0;
+int __PIInit_Initializer__::count_            = 0;
 PIInit * __PIInit_Initializer__::__instance__ = nullptr;
 
 __PIInit_Initializer__::__PIInit_Initializer__() {
@@ -71,8 +76,8 @@ __PIInit_Initializer__::~__PIInit_Initializer__() {
 	}
 }
 
-#endif
-#endif
+#	endif
+#  endif
 
 
 //! \~\ingroup Core