Add libmobi fuzzing integration

[S3DFX-CYBER]

libmobi is a C library for
reading, writing, and converting MOBI/KF8/KF7 ebook files. It is used
by widely deployed tools including Calibre and KOReader to process
user-supplied ebook files, making it a meaningful target for malformed
input fuzzing.

Fuzz Targets

Target	Surface covered
fuzz_load	mobi_load_file() — PalmDB header, record list, MOBI/EXTH header parsing
fuzz_parse_rawml	Full two-phase pipeline — HTML reconstruction, CSS parsing, OPF generation, resource extraction
fuzz_huffman	Huffman-CDIC decompression path via full document load

Build System

autotools (./autogen.sh + ./configure + make)
Static library build with --disable-shared --enable-static

Local Testing

All three fuzz targets were built and run locally using the OSS-Fuzz
helper before submission:
python3 infra/helper.py build_image libmobi ✓
python3 infra/helper.py build_fuzzers libmobi ✓
python3 infra/helper.py run_fuzzer libmobi fuzz_load ✓
python3 infra/helper.py run_fuzzer libmobi fuzz_parse_rawml ✓
python3 infra/helper.py run_fuzzer libmobi fuzz_huffman ✓

Tested with FUZZING_ENGINE=libfuzzer and SANITIZER=address on
linux/amd64.

Why libmobi qualifies

• Parses untrusted binary input (MOBI/KF8 ebook files) from
  user-supplied sources
• C codebase — high value for memory safety fuzzing
• Prior CVEs found via fuzzing (CVE-2022-1533, CVE-2022-1534) confirm
  real bug surface exists
• Used downstream by Calibre (20M+ downloads) and KOReader

[github-actions]

S3DFX-CYBER is integrating a new project:
- Main repo: https://github.com/bfabiszewski/libmobi.git
- Criticality score: 0.28204