feat(api): pin response_model on dict-returning mutation routes

Every mutation route that returned an untyped dict now declares
response_model at the decorator. MessageResponse covers the eight
{"message": ...} envelopes (change-password, mutate-decky, mutate-
interval, update-deployment-limit, update-global-mutation-interval,
delete-user, update-user-role, reset-user-password). Purpose-built
models cover the richer shapes (DeployResponse for /deckies/deploy,
PurgeResponse for /config/reinit, ReapReportResponse for /reap-orphans,
UserResponse for /config/users). 204-No-Content and Response/
ORJSONResponse routes stay as-is.

The wire shape for clients is unchanged — the envelopes already only
shipped a message field. What changes is that a handler which
accidentally returns a richer dict (e.g. a full user row including
password_hash) would be silently stripped to the declared fields at
serialization time.

Also flips F4/D "expensive LIKE" to accepted (new DA-09) — the /logs
and /attackers search routes LIKE-scan unbounded columns, but both are
admin-gated, limit-capped, and operator rate-limit scope per DA-04.
FTS5 stays a performance TODO, not a security blocker.

decnet/web/db/models/__init__.py

@@ -11,6 +11,9 @@ from ._base import (
     _BIG_TEXT,
     _normalize_null,
 )
+from .common import (
+    MessageResponse,
+)
 from .auth import (
     AdminConfigResponse,
     ChangePasswordRequest,
@@ -34,7 +37,9 @@ from .attackers import (
 )
 from .deploy import (
     DeployIniRequest,
+    DeployResponse,
     MutateIntervalRequest,
+    PurgeResponse,
 )
 from .health import (
     ComponentHealth,
@@ -82,6 +87,7 @@ from .topology import (
     NextIPResponse,
     NextSubnetResponse,
     NotEditableResponse,
+    ReapReportResponse,
     ServiceCatalogResponse,
     Topology,
     TopologyDecky,
@@ -120,6 +126,8 @@ __all__ = [
     "NullableString",
     "_BIG_TEXT",
     "_normalize_null",
+    # common
+    "MessageResponse",
     # auth
     "AdminConfigResponse",
     "ChangePasswordRequest",
@@ -141,7 +149,9 @@ __all__ = [
     "SmtpTarget",
     # deploy
     "DeployIniRequest",
+    "DeployResponse",
     "MutateIntervalRequest",
+    "PurgeResponse",
     # health
     "ComponentHealth",
     "HealthResponse",
@@ -185,6 +195,7 @@ __all__ = [
     "NextIPResponse",
     "NextSubnetResponse",
     "NotEditableResponse",
+    "ReapReportResponse",
     "ServiceCatalogResponse",
     "Topology",
     "TopologyDecky",

decnet/web/db/models/common.py

@@ -0,0 +1,15 @@
+"""Generic response shapes used across multiple router domains."""
+from __future__ import annotations
+
+from pydantic import BaseModel
+
+
+class MessageResponse(BaseModel):
+    """Standard envelope for mutations whose only payload is a status message.
+
+    Pinning the wire shape at the decorator (``response_model=MessageResponse``)
+    prevents a handler that accidentally returns a richer dict — e.g. a user
+    row with ``password_hash`` — from leaking extra fields to the client.
+    """
+
+    message: str

decnet/web/db/models/deploy.py

@@ -17,3 +17,13 @@ class DeployIniRequest(BaseModel):
     # This field now enforces strict INI structure during Pydantic initialization.
     # The OpenAPI schema correctly shows it as a required string.
     ini_content: IniContent = PydanticField(..., description="A valid INI formatted string")
+
+
+class DeployResponse(BaseModel):
+    message: str
+    mode: str
+
+
+class PurgeResponse(BaseModel):
+    message: str
+    deleted: dict[str, int]

decnet/web/db/models/topology.py

@@ -420,3 +420,11 @@ class DeployAcceptedResponse(BaseModel):
     topology_id: str
     status: str
     dry_run: bool = False
+
+
+class ReapReportResponse(BaseModel):
+    live_prefixes: list[str]
+    orphan_prefixes: list[str]
+    containers_removed: list[str]
+    networks_removed: list[str]
+    errors: list[str]