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.

decnet/web/router/swarm/__init__.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """Swarm controller routers.
 
 One file per endpoint, aggregated under the ``/swarm`` prefix. Mounted

decnet/web/router/swarm/api_check_hosts.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """POST /swarm/check — active mTLS probe of every enrolled worker.
 
 Updates ``SwarmHost.status`` and ``last_heartbeat`` for each host based

decnet/web/router/swarm/api_decommission_host.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """DELETE /swarm/hosts/{uuid} — decommission a worker.
 
 Removes the DeckyShard rows bound to the host (portable cascade — MySQL

decnet/web/router/swarm/api_deploy_swarm.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """POST /swarm/deploy — shard a DecnetConfig across enrolled workers.
 
 Per worker we build a filtered copy containing only the deckies assigned

decnet/web/router/swarm/api_enroll_host.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """POST /swarm/enroll — issue a worker cert bundle and register the host.
 
 Enrollment is master-driven: the controller holds the CA private key,

decnet/web/router/swarm/api_get_host.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """GET /swarm/hosts/{uuid} — fetch a single worker by UUID."""
 from __future__ import annotations
 

decnet/web/router/swarm/api_get_swarm_health.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """GET /swarm/health — controller liveness (no I/O)."""
 from __future__ import annotations
 

decnet/web/router/swarm/api_heartbeat.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """POST /swarm/heartbeat — agent→master liveness + decky snapshot refresh.
 
 Workers call this every ~30 s with the output of ``executor.status()``.

decnet/web/router/swarm/api_list_deckies.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """GET /swarm/deckies — list decky shards with their worker host's identity.
 
 The DeckyShard table maps decky_name → host_uuid; users want to see which

decnet/web/router/swarm/api_list_hosts.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """GET /swarm/hosts — list enrolled workers, optionally filtered by status."""
 from __future__ import annotations
 

decnet/web/router/swarm/api_teardown_swarm.py

@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
 """POST /swarm/teardown — tear down one or all enrolled workers."""
 from __future__ import annotations