Adopt libbs2b: 3.1.0+dfsg1 (Closes: #1007187)

Adoption of orphaned package (Maintainer -> me). Switch to active upstream fork; repack to +dfsg1 removing win32/ and autogen.sh (DFSG cleanliness, smaller delta).

Commit structure:

Import upstream 3.1.0+dfsg1 (repacked fork)

Debianization refresh (control/rules/watch/changelog, gbp.conf, maintainer change)

Patch stack prune & update (DEP-3)

QA: symbols file, autopkgtests (smoke + compile), upstream metadata, salsa-ci config

Patch stack (remaining):

drop-win32-subdir.patch (remove dead dir reference)

remove-win32-references.patch (configure cleanup)

missing_math_lib.patch (add -lm via LIBADD; to forward upstream)

Autopkgtests:

smoke: binary presence + help exit handling + library discoverability

compile: -dev usability (simple compile/link)

Symbols:

debian/libbs2b0.symbols added; no Debian rev suffixes.

Reproducibility:

pristine-tar reproduces orig tarball.

gbp source build clean.

SHA256:

dsc: c452f69790023ed768b9f5de91f9b9e2cc34edf58551c8c9cc5cd5af481f2b5b

debian.tar.xz: 9e18d2c79bc9c662a5a5c6377d2b13eacee7fb8eb5a6e9a433b1f0308b342d78

orig.tar.xz: 7175fab575df45027d119b7f4ee3aa966a14055ca478eae6abf7191faa2ea97f

Watch: updated (git mode, Files-Excluded for win32/ autogen.sh).

gbp: pristine-tar + signed tags enabled.

Deferred (future WIP):

Manpages for bs2bconvert / bs2bstream Forward missing_math_lib.patch upstream (drop once merged) Broader functional autopkgtest (audio transform)

Closes: #1007187

Please review & sponsor. Let me know if you prefer the adoption squashed to fewer commits.