refactor: modernize fit2x - own L-BFGS, remove LabVIEW layer and ALGLIB, BSD-3 SPDX

Optimizer:
- Replace the bundled FORTRAN-derived L-BFGS (Nocedal/ALGLIB translation,
  non-OSI citeware license) and the entire thirdparty/alglib tree (compiled
  wholesale but used only for its array type) with a self-contained,
  header-only, std-only L-BFGS in include/i_lbfgs.h (BSD-3, ~150 lines:
  two-loop recursion, Armijo backtracking, central-difference gradients).
  The bfgs class interface (target function, fixed-parameter masks, eps and
  iteration control, minimize info codes) is unchanged, so DecayFit23-26
  and the 2D Gaussian image localization work without call-site changes.

fit2x cleanup:
- Remove the LabView-heritage interface: LVI32Array, LVDoubleArray, MParam,
  CreateMParam and CreateLV*Array are gone. The fits now use DecayFitData,
  a plain std::vector container (Jordi format sizing preserved) that maps
  directly to numpy via SWIG. The x/fixed parameter array layouts of
  DecayFitNN::fit/modelf/targetf are unchanged.
- Fix an uninitialized stack read in DecayFit25::correct_input (gamma was
  read from xm[1] before ever being written), which made fit25 results
  depend on the process memory layout. Fit results are now reproducible
  across processes.
- Make all fit-internal static state thread_local.
- New one-call convenience API: tttrlib.fit23/fit24/fit25/fit26 functions
  with keyword arguments, sensible defaults and dict results; the
  Fit23-Fit26 wrapper classes stay unchanged.

Licensing:
- Consistent BSD-3-Clause: fix the stray MIT SPDX tag in DecayFit.h and
  add SPDX-License-Identifier: BSD-3-Clause to all project sources
  (include/, src/, ext/python/). No third-party optimizer code remains.

Verified: fit model functions bit-identical; fit quality (2I*) equal or
better than the previous optimizer on a multi-start grid; full test suite
passes (616); fit23 throughput ~15k fits/s.

Author: tpeulen

CMakeLists.txt

@@ -194,14 +194,6 @@ ELSE()
   LINK_LIBRARIES(nlohmann_json::nlohmann_json)
 ENDIF()
 
-# LBFGS
-FILE(GLOB_RECURSE LBFGS "${CMAKE_CURRENT_SOURCE_DIR}/thirdparty/lbfgs/*.cpp")
-LIST(APPEND SRC_files ${LBFGS})
-
-# ALGLib
-FILE(GLOB_RECURSE ALGLIB "${CMAKE_CURRENT_SOURCE_DIR}/thirdparty/alglib/*.cpp")
-LIST(APPEND SRC_files ${ALGLIB})
-
 # HighFive HDF5 reader
 IF(BUILD_PHOTON_HDF)
   IF(EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/thirdparty/HighFive/CMakeLists.txt")

examples/fluorescence_decay/plot_fit23_usage_2.py

@@ -57,8 +57,8 @@ def model_irf(
 # add poisson noise to model and use as data
 data = np.random.poisson(model * n_photons)
 
-# create MParam structure that contains all parameters for fitting
-m_param = tttrlib.CreateMParam(
+# create DecayFitData container that contains all parameters for fitting
+m_param = tttrlib.DecayFitData(
     irf=irf_np,
     background=bg,
     data=data.astype(np.int32),

ext/documentation.i

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 
 // File: index.xml
 

ext/python/BurstFeatureExtractor.i

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 %{
 #include "BurstFeatureExtractor.h"
 #include <nlohmann/json.hpp>

ext/python/BurstFilter.i

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 %{
 #include "BurstFilter.h"
 #include "Channel.h"

ext/python/CLSM.i

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 %{
 #include "CLSMPixel.h"
 #include "CLSMLine.h"

ext/python/CLSMFrame.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: BSD-3-Clause
 import numpy as np
 
 @property

ext/python/CLSMISM.i

@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: BSD-3-Clause
 // CLSMISM SWIG interface (embedded into the main tttrlib module)
 %include "misc_types.i"
 

ext/python/CLSMISM.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: BSD-3-Clause
 import warnings
 import numpy as np
 

ext/python/CLSMImage.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: BSD-3-Clause
 import numpy as np
 
 @property