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/application/pisingleapplication.cpp

@@ -24,6 +24,7 @@
 #include "pisharedmemory.h"
 #include "pitime.h"
 
+#ifndef PIP_NO_THREADS
 
 //! \class PISingleApplication pisingleapplication.h
 //! \~\details
@@ -64,7 +65,7 @@
 //!
 
 
-#define SHM_SIZE 32_KiB
+#  define SHM_SIZE 32_KiB
 
 
 PISingleApplication::PISingleApplication(const PIString & app_name): PIThread() {
@@ -150,3 +151,5 @@ void PISingleApplication::waitFirst() const {
 	while (!started)
 		piMSleep(50);
 }
+
+#endif // PIP_NO_THREADS