ALICE3 Forward Detector update

[pkurash]

Updated code for ALICE3 Forward Detector (FD).

1. Scintillator modules placed closer to the interaction point
2. Modified eta coverage
3. Two extra Cherenkov radiator arrays

For more details, see my presentation at 7th Upgrade Week:

[njacazio]

Thanks a lot @pkurash ! Here a couple of minor suggestions

[alibuild]

Error while checking build/O2/fullCI_slc9 for 4706dc8 at 2026-09-13 07:44:

## sw/BUILD/o2checkcode-latest/log
--
========== List of errors found ==========
++ GRERR=0
++ grep -v clang-diagnostic-error error-log.txt
++ grep ' error:'
/sw/SOURCES/O2/slc9_x86-64-slc9_x86-64/0/Detectors/Upgrades/ALICE3/FD3/simulation/src/Detector.cxx:408:12: error: statement should be inside braces [readability-braces-around-statements]
++ [[ 0 == 0 ]]
++ exit 1
--

Full log here.

[alibuild]

Error while checking build/O2/fullCI_slc9 for 26ef75b at 2026-09-20 20:56:

No log files found

Full log here.

[vkucera]

@pkurash Please make the PR title more informative. There are plenty places in O2 where one could add a new geometry.

[alibuild]

Error while checking build/O2/fullCI_slc9 for 3101309 at 2026-09-23 20:38:

No log files found

Full log here.