Rename Installation to Instance

Follows the portal: the noun is "instance" everywhere the app says it —
UI strings, CLI output, error details, docs and comments. The wire keys
(`instance_id`, `instance_token`) and the hub route this calls move with it.

An existing cloud.json is adopted rather than refused: without the key
alias the dataclass fails to parse, which the caller swallows and reads as
"never enrolled" instead of "reconnect".

`instance_key` on a node type becomes `target_key`. It means the outside
thing a node points at, which is a different sense of the word, and keeping
both would put two meanings of "instance" in one codebase.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015YrQnKV3bnQd4K342y8tKj

backend/tests/flow/test_brain_graph.py

@@ -78,7 +78,7 @@ def test_an_edge_carries_the_qualified_message(controller: FlowController):
 def test_a_credential_never_reaches_the_key():
     # Stored params, so a secret is still a reference. Neither its name nor its
     # value belongs in something the browser gets to see.
-    key = MqttNode.instance_key({**BROKER, "password": {"$secret": "broker_pw"}})
+    key = MqttNode.target_key({**BROKER, "password": {"$secret": "broker_pw"}})
 
     assert key == "mosquitto:1883/sensors/temp"
 

backend/tests/flow/test_dashboards.py

@@ -423,7 +423,7 @@ def test_an_unbound_setting_is_just_its_value():
 
     No message means nothing to type-check and nothing for a panel to be
     entitled to — and a name this build does not know is left alone rather
-    than refused, so an older installation reads a newer document.
+    than refused, so an older instance reads a newer document.
     """
     defn = DashboardDef(
         name="house",
@@ -523,7 +523,7 @@ def test_a_chart_of_runs_must_say_which_runs_and_which_metric():
 
 
 def test_a_document_written_as_pages_is_read_as_one_grid():
-    """Stored dashboards live in each installation's repository.
+    """Stored dashboards live in each instance's repository.
 
     So the old shape is normalised on the way in rather than migrated, and a
     placed second section keeps its arrangement instead of piling onto the

backend/tests/flow/test_provision.py

@@ -192,7 +192,7 @@ def test_a_node_waiting_for_a_machine_asks_for_one_once(monkeypatch):
     assert ran.is_set()
 
 
-def test_an_installation_with_nowhere_to_start_one_has_no_file(tmp_path):
+def test_an_instance_with_nowhere_to_start_one_has_no_file(tmp_path):
     assert load_provisioners(tmp_path / "provisioners.json") == []
 
 

backend/tests/flow/test_runtime_control.py

@@ -237,7 +237,7 @@ def lifecycle(monkeypatch: pytest.MonkeyPatch) -> list[str]:
 def test_rebuilding_one_flow_leaves_another_flows_node_running(
     tmp_path: Path, lifecycle: list[str]
 ):
-    """The whole point: reconnecting one flow's nodes, not the installation's."""
+    """The whole point: reconnecting one flow's nodes, not the instance's."""
     store = FlowStore(tmp_path / "flows")
     for name in ("a", "b"):
         store.write_flow(FlowDef(name=name, nodes=[NodeDef(id="io", type="lifecycle")]))

backend/tests/flow/test_vocabulary.py

@@ -1,6 +1,6 @@
 """What the flow-logic nodes actually do.
 
-These are the shapes a Node-RED installation is mostly made of, so their
+These are the shapes a Node-RED instance is mostly made of, so their
 behaviour is worth pinning rather than just their construction.
 """
 

backend/tests/flow/test_webpush.py

@@ -16,7 +16,7 @@ from fluksio.flow import webpush
 
 @pytest.fixture(autouse=True)
 def store(tmp_path, monkeypatch):
-    """A store per test, so nothing writes into the real installation."""
+    """A store per test, so nothing writes into the real instance."""
     monkeypatch.setattr(settings, "WEBPUSH_FILE", tmp_path / "webpush.json")
     return tmp_path / "webpush.json"