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/system/pisystemtests.cpp

@@ -19,9 +19,9 @@
 
 #include "pisystemtests.h"
 
-#ifndef MICRO_PIP
+#ifndef PIP_NO_FILESYSTEM
 #  include "piconfig.h"
-#endif
+#endif // !PIP_NO_FILESYSTEM
 
 
 namespace PISystemTests {
@@ -35,10 +35,10 @@ PISystemTestReader pisystestreader;
 
 
 PISystemTests::PISystemTestReader::PISystemTestReader() {
-#if !defined(WINDOWS) && !defined(MICRO_PIP)
+#if !defined(WINDOWS) && !defined(PIP_NO_FILESYSTEM)
 	PIConfig conf(PIStringAscii("/etc/pip.conf"), PIIODevice::ReadOnly);
 	time_resolution_ns = conf.getValue(PIStringAscii("time_resolution_ns"), 1).toLong();
 	time_elapsed_ns    = conf.getValue(PIStringAscii("time_elapsed_ns"), 0).toLong();
 	usleep_offset_us   = conf.getValue(PIStringAscii("usleep_offset_us"), 60).toLong();
-#endif
+#endif // !WINDOWS && !PIP_NO_FILESYSTEM
 }