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/fluksio/core/bootstrap.py

@@ -1,6 +1,6 @@
 """First run: an account to sign in with.
 
-An installation started from the command line is given no environment, so the
+An instance started from the command line is given no environment, so the
 superuser a deployment sets in `.env` has to come from somewhere. The session
 key is the CLI's own business — it has to be set before this module can be
 imported at all.
@@ -27,7 +27,7 @@ def ensure_superuser(
     """The account to sign in with, made on first run.
 
     Returns the user and, when it was just created, the password in clear —
-    the caller prints it once. An installation that already has a superuser is
+    the caller prints it once. An instance that already has a superuser is
     left alone: this is a first run, not a password reset.
     """
     existing = session.exec(
@@ -57,7 +57,7 @@ def pick_superuser(session: Session, email: str | None = None) -> User:
         select(User).where(User.is_superuser == True)  # noqa: E712
     ).all()
     if not users:
-        raise LookupError("This installation has no superuser to enrol as")
+        raise LookupError("This instance has no superuser to enrol as")
     if len(users) > 1:
         addresses = ", ".join(sorted(u.email for u in users))
         raise LookupError(f"Several superusers here — name one with --as: {addresses}")

backend/fluksio/core/config.py

@@ -54,7 +54,7 @@ class Settings(BaseSettings):
     FRONTEND_HOST: str = "http://localhost:5173"
     ENVIRONMENT: Literal["local", "staging", "production"] = "local"
 
-    #: Everything this installation keeps: the database, the flow repository,
+    #: Everything this instance keeps: the database, the flow repository,
     #: secrets, artifacts and the user venv. The paths below derive from it
     #: unless they are set explicitly.
     DATA_DIR: Path = Path("flow-data")
@@ -72,13 +72,13 @@ class Settings(BaseSettings):
     # Which failures reach which channel. Beside the flows, not in them:
     # alerting is the deployment's concern, not any one flow's.
     ALERTS_FILE: Path = Path("flow-data/alerts.json")
-    # This installation's web push keypair and the browsers subscribed to it.
+    # This instance's web push keypair and the browsers subscribed to it.
     # Beside the alerts it serves; deleting it makes every device subscribe
     # again.
     WEBPUSH_FILE: Path = Path("flow-data/webpush.json")
     # Where machines can be started from when a node needs one and nothing that
     # could take it is attached. Operator-authored, like the alerts beside it,
-    # and absent on an installation that has nowhere to start one.
+    # and absent on an instance that has nowhere to start one.
     PROVISIONERS_FILE: Path = Path("flow-data/provisioners.json")
     # Which dashboards each device shows. Beside the flows for the same reason
     # alerting is: where a screen hangs is the deployment's concern rather than
@@ -99,7 +99,7 @@ class Settings(BaseSettings):
     PRIVATE_API_ENABLED: bool = False
     DOMAIN: str = "localhost"
     OAUTH_PRIVATE_KEY_FILE: Path = Path("flow-data/oauth-key.pem")
-    # Written only when someone enrols this installation with a portal.
+    # Written only when someone enrols this instance with a portal.
     # Its absence is what keeps remote access off.
     CLOUD_CONFIG_FILE: Path = Path("flow-data/cloud.json")
     OAUTH_CODE_EXPIRE_SECONDS: int = 60
@@ -113,7 +113,7 @@ class Settings(BaseSettings):
     # because a limit somebody set and did not get is the worse surprise.
     FLOW_MAX_WORKERS: PositiveInt = 4
     # How many cascades may be in flight at once. Sustained throughput is this
-    # over the mean cascade time, so an installation whose nodes wait on the
+    # over the mean cascade time, so an instance whose nodes wait on the
     # network rather than on a CPU wants it higher than the core count.
     FLOW_MAX_CASCADES: PositiveInt = 4
     # How many batch runs are driven at once. A different limit from the one

backend/fluksio/core/db.py

@@ -142,9 +142,9 @@ def init_db(session: Session) -> None:
         user = crud.create_user(session=session, user_create=user_in)
 
 
-#: The sizes an installation starts with. Written once, when there are none,
+#: The sizes an instance starts with. Written once, when there are none,
 #: and editable from there — what a name means is a property of the machines
-#: this installation has, and nothing here knows what those are.
+#: this instance has, and nothing here knows what those are.
 SEED_FLAVORS: tuple[dict[str, Any], ...] = (
     {"name": "small", "cpus": 1, "ram": 2048, "description": "A poll, a threshold"},
     {"name": "medium", "cpus": 4, "ram": 8192, "description": "A step that computes"},
@@ -160,7 +160,7 @@ SEED_FLAVORS: tuple[dict[str, Any], ...] = (
 
 
 def seed_flavors(session: Session) -> None:
-    """Give a new installation sizes to pick from, once.
+    """Give a new instance sizes to pick from, once.
 
     Only when there are none at all: they are editable, and re-adding one that
     somebody deliberately removed would be an argument nobody can win.