v4.1.0: source-only build, multithreaded-encryption fix, security hardening

Build from source with no vendored binaries:
- Remove prebuilt libzuptsdk.so / libpqvaptvupt.so (and a stray .pyc). The
  default build needs only a C compiler + make; it links no external library
  and installs no .so. The libzuptsdk-backed modes (Argon2id KDF, --pq-sdk,
  --pq-box) are gated behind an opt-in `make WITH_SDK=1`. The default password
  KDF is PBKDF2-SHA256 and --pq (native ML-KEM-768 + X25519) is the built-in PQ
  mode. openSUSE/RPM/deb/AUR/Homebrew/Nix recipes bumped to 4.1.0; the openSUSE
  spec now builds source-only (%files ships no .so, %build/%install WITH_SDK=0).

Fix: multithreaded encrypted archives were unextractable on the native AEAD
path. The parallel compress/decompress workers skipped the F-09 frame-preface
AAD that the serial path and the archive's AAD_PREFACE flag bind into every
block MAC, so each multithreaded block failed authentication. The workers now
bind the preface via a shared serializer; output is byte-identical across
thread counts and interoperates with single-threaded archives (also fixes
`--kdf pbkdf2 -t N` in any build).

Security hardening (crafted-archive memory safety + crypto):
- LZH raw code-length stack overflow + huff_lut OOB write
- overflow-safe bounds in parse_index and solid-mode extract (heap OOB read)
- SEQ decoder safe-zone heap overflow (litlen+matchlen reserve)
- require the per-block ENCRYPTED flag on encrypted archives (plaintext forgery)
- cap archive-supplied PBKDF2 iteration count (KDF-amplification DoS)
- non-elidable secret wipe in the SDK path; restored disk images created 0600

Docs: remove AUDIT.md / BENCHMARKS.md / ROADMAP.md; trim marketing/AI-styled
text and correct KDF/PQ facts across README, SECURITY, INSTALL, DISTRIBUTION,
THREAT_MODEL, THIRD-PARTY-NOTICES, the man page, and packaging READMEs. Wire
format v1.6 unchanged.

gui/README.md

@@ -1,4 +1,4 @@
-# VaptVupt GUI — Cross-Platform Post-Quantum Backup
+# VaptVupt GUI
 
 Desktop application for [vaptvupt](https://git.securityops.co/cristiancmoises/vaptvupt) backup compression with ML-KEM-768 + X25519 post-quantum hybrid encryption.
 
@@ -14,9 +14,6 @@ tar xzf vaptvupt-gui.tar.gz && cd vaptvupt-gui
 ./install.sh --user              # adds right-click menu integration
 ```
 
-After install, right-click any file in Nemo/Nautilus to see "Compress with VaptVupt".
-Double-click any .zupt file to open it in the GUI.
-
 ### Windows
 
 **Option A — Installer (recommended):**
@@ -119,7 +116,7 @@ The GUI calls the vaptvupt CLI binary — all cryptography runs in native C, not
 
 ## Credits
 
-- **vaptvupt** v2.2.3 — Cristian Cezar Moisés ([github](https://git.securityops.co/cristiancmoises/vaptvupt))
+- **vaptvupt** v4.1.0 — Cristian Cezar Moisés ([github](https://git.securityops.co/cristiancmoises/vaptvupt))
 
 ## License