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/service_testing/__init__.py

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

tests/service_testing/conftest.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Shared helpers for binary-protocol service tests.
 """

tests/service_testing/test_dns.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for decnet/templates/dns/server.py and decnet/services/dns.py."""
 
 import collections

tests/service_testing/test_imap.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/imap/server.py
 

tests/service_testing/test_imap_spool.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Seed-backed email loading for the IMAP template.
 
 Verifies that when ``IMAP_EMAIL_SEED`` points at a directory of .eml /

tests/service_testing/test_instance_seed.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/instance_seed.py — the per-instance stealth
 seeding helper. These tests pin NODE_NAME to assert determinism of the

tests/service_testing/test_mongodb.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/mongodb/server.py
 

tests/service_testing/test_mqtt.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/mqtt/server.py
 

tests/service_testing/test_mqtt_fuzz.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/mqtt/server.py — protocol boundary and fuzz cases.
 

tests/service_testing/test_mssql.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/mssql/server.py
 

tests/service_testing/test_mysql.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/mysql/server.py
 

tests/service_testing/test_pop3.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/pop3/server.py
 

tests/service_testing/test_pop3_spool.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Seed-backed email loading for the POP3 template.
 
 Concat semantics: hardcoded ``_BAIT_EMAILS`` + .eml/.json from the seed

tests/service_testing/test_postgres.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/postgres/server.py
 

tests/service_testing/test_rdp_basic.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for decnet/templates/rdp/server.py — X.224 CR cookie capture.
 
 Drives the asyncio handler with an in-memory StreamReader, asserts:

tests/service_testing/test_rdp_nla.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for the RDP NLA / CredSSP credential-capture path.
 
 The TLS layer is exercised end-to-end in deploy verification; here we

tests/service_testing/test_redis.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 import importlib.util
 import sys
 from types import ModuleType

tests/service_testing/test_smb_server.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Tests for decnet/templates/smb/server.py — hand-rolled SMB2 framer.
 
 Drives the asyncio handler with an in-memory StreamReader and a mocked

tests/service_testing/test_smtp.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/smtp/server.py
 

tests/service_testing/test_snmp.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """
 Tests for decnet/templates/snmp/server.py