feat: restore ldb_query_raw shared-library query entry point

[scanoss-qg]

Why

The new_hash refactor removed src/ldb_wrapper.c, which defined ldb_query_raw — the single-key shared-library entry point that third-party consumers link libldb.so against (e.g. the Go cgo binding used by scanoss.api). On this branch the only remaining query surface is the interactive CLI (shell/command), so a process embedding libldb.so has no programmatic way to read a table. This restores that entry point, adapted to the current architecture.

What

Two additive files (src/ldb_wrapper.{c,h}), picked up automatically by the Makefile's src/*.c wildcard; libldb.so then exports ldb_query_raw and ldb_dump_row.

• ldb_query_raw(dbtable, key) — validates the table, reads its .cfg, checks the hex key against the table's key_ln (or the 32-bit main key), and collects every matching record via ldb_fetch_recordset.
• ldb_dump_row(...) — record handler matching the current ldb_record_handler_t signature (struct ldb_table * first arg, no int subkey_ln). Frames each record as [uint32 size][payload] into a growable T_RawRes.

Because key length is .cfg-driven, both MD5 (16-byte) and CRC64 (8-byte) tables work with no code change.

Hardening over the historical wrapper

The version that existed pre-new_hash had a few rough edges; this restores it fixed:

• Ownership: no longer free()s the caller-owned dbtable argument (ldb_read_cfg copies it internally — it was never the callee's to free).
• No exit() in a library: a failed realloc now stops iteration and returns the partial result instead of exit(EXIT_FAILURE) killing the host process.
• Buffer growth: the grow check now accounts for the 4-byte size prefix (the old check compared payload size only while writing size + 4 — a potential 4-byte overrun at the boundary).
• Diagnostics: routed through logger (log_info) instead of printf; dropped an unused allocation.

Testing

• Builds clean with make / make lib (-Wall, no new warnings); objdump -T libldb.so shows ldb_query_raw / ldb_dump_row exported, and the ldb CLI links unchanged.
• Validated end-to-end against a real CRC64 knowledge base (the ossv2 pivot → file → path chain) through the downstream scanoss.api LDB read path.

Follow-ups (out of scope here)

• A shared-library-level test for ldb_query_raw (the current test/ suite exercises the CLI via bash_unit; there's precedent in test/null_sector_test.c for a C test).
• Downstream consumers that relied on the old wrapper freeing dbtable must free their own argument after re-vendoring (the correct ownership).
• Release builds of libldb.so should target the oldest supported glibc for portability across consumer hosts.