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/collector/__init__.py

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

tests/collector/test_collector.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for the host-side Docker log collector."""
 
 import json

tests/collector/test_collector_bus.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Bus wiring for the collector (DEBT-031, worker 5).
 
 Collector streams logs from Docker containers in a thread pool — can't be

tests/collector/test_collector_thread_pool.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Verify that the collector and sniffer use dedicated thread pools
 instead of the default asyncio executor — preventing starvation of
 short-lived ``asyncio.to_thread`` calls in the web API layer."""

tests/collector/test_parse_rfc5424_double_wrap.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Collector parser unwraps double-wrapped RFC5424 lines.
 
 Honeypot SSH containers export a ``PROMPT_COMMAND`` that calls

tests/collector/test_session_aggregator.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Collector session aggregator emits ``attacker.session.ended``.
 
 Pins the producer-side fix that closes the gap surfaced in TTP

tests/collector/test_session_ended_publish.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Collector publishes ``attacker.session.ended`` end-to-end.
 
 Wires :func:`_make_system_log_publisher` against a fake bus, drives