chore: relicense to AGPL-3.0-or-later and add SPDX headers

Replaces LICENSE (GPLv3 -> AGPLv3) and prepends
`SPDX-License-Identifier: AGPL-3.0-or-later` to every source file
across decnet/, decnet_web/, tests/, scripts/, and tools/.

Rationale: closes the GPLv3 ASP loophole so any party operating a
modified DECNET as a network service must offer their modified
source. Personal copyright (Samuel Paschuan) + inbound=outbound
contributions make a future unilateral relicense infeasible.

- LICENSE: full AGPL-3.0 text (gnu.org/licenses/agpl-3.0.txt)
- COPYRIGHT: project copyright notice
- tools/add_spdx_headers.py: idempotent header injector
  (shebang- and PEP 263-aware)

Touches 1565 source files (.py, .ts, .tsx, .js, .jsx, .css, .sh).
No behavior change; comments only.

tests/sniffer/__init__.py

@@ -0,0 +1 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later

tests/sniffer/test_ipv6_leak.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Passive IPv6 link-local leak detection — sniffer unit tests.
 
 Tests SnifferEngine._on_ipv6_packet and _ipv6_iid_classify via direct

tests/sniffer/test_ja4h.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for _ja4h computation and QUIC helpers in decnet.sniffer.fingerprint."""
 from __future__ import annotations
 

tests/sniffer/test_ja4h_with_real_order.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Verify that JA4H computed from canonical header order (as emitted by the
 decnet_fp listener wrapper via syslog_bridge._compute_ja4h) matches the

tests/sniffer/test_quic_initial.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for QUIC v1 Initial packet key derivation (RFC 9001 Appendix A vectors)."""
 from __future__ import annotations
 

tests/sniffer/test_sniffer_bus.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Bus wiring for the fleet sniffer (DEBT-031, worker 1).
 
 The sniff loop itself lives in a dedicated thread running scapy and

tests/sniffer/test_sniffer_ja3.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Unit tests for the JA3/JA3S parsing logic in decnet/templates/sniffer/server.py.
 

tests/sniffer/test_sniffer_p0f.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Unit tests for the passive p0f-lite OS fingerprint lookup.
 

tests/sniffer/test_sniffer_retransmit.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Unit tests for TCP retransmit detection in the SnifferEngine flow aggregator.
 

tests/sniffer/test_sniffer_seq_class.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Unit tests for decnet.sniffer.seq_class.classify_sequence.
 

tests/sniffer/test_sniffer_tcp_fingerprint.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Integration tests for TCP-level passive fingerprinting in the SnifferEngine.
 

tests/sniffer/test_sniffer_worker.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for the fleet-wide sniffer worker and fingerprinting engine.