feat(pilot): PATCH /suggested-fixes/:id/outcome endpoint + tests

Records engineer-reported outcome (applied_success|applied_failed|
applied_partial|dismissed). Enforces transition rules (partial → success/
failed allowed; terminal outcomes return 409) and notes requirements
(applied_partial requires notes).

Sets verified_at on success/failure, stamps applied_at if not already
set (handles the case where the AI [FIX_OUTCOME] marker fires before
the engineer clicks Apply).

Also fixes pre-existing test-infrastructure bug: network_diagram.py used
bare string server_default="'[]'" for JSONB columns, which asyncpg
rejects during test schema creation. Changed to text("'[]'::jsonb") to
match the pattern used by script_template.py.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/models/network_diagram.py

@@ -3,7 +3,7 @@ import uuid
 from datetime import datetime, timezone
 from typing import Any, TYPE_CHECKING
 
-from sqlalchemy import String, Text, Boolean, DateTime, ForeignKey
+from sqlalchemy import String, Text, Boolean, DateTime, ForeignKey, text
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from sqlalchemy.dialects.postgresql import UUID, JSONB
 
@@ -30,8 +30,8 @@ class NetworkDiagram(Base):
     client_name: Mapped[str | None] = mapped_column(String(255), nullable=True)
     asset_name: Mapped[str | None] = mapped_column(String(255), nullable=True)
     description: Mapped[str | None] = mapped_column(Text, nullable=True)
-    nodes: Mapped[list[dict[str, Any]]] = mapped_column(JSONB, nullable=False, server_default="'[]'")
-    edges: Mapped[list[dict[str, Any]]] = mapped_column(JSONB, nullable=False, server_default="'[]'")
+    nodes: Mapped[list[dict[str, Any]]] = mapped_column(JSONB, nullable=False, server_default=text("'[]'::jsonb"))
+    edges: Mapped[list[dict[str, Any]]] = mapped_column(JSONB, nullable=False, server_default=text("'[]'::jsonb"))
     thumbnail_url: Mapped[str | None] = mapped_column(Text, nullable=True)
     is_archived: Mapped[bool] = mapped_column(
         Boolean, nullable=False, default=False,