fix(models): rename sqlalchemy.text import to avoid shadowing by InvariantModel text column

The InvariantModel class defined a Column named "text" which shadowed the
sqlalchemy.text() function used in server_default, postgresql_where, and
sqlite_where expressions. Renamed the import from "text" to "sa_text" and
updated all 4 usages.

ISSUES CLOSED: #8573

src/cleveragents/infrastructure/database/models.py

@@ -61,7 +61,7 @@ from sqlalchemy import (
     Text,
     UniqueConstraint,
     create_engine,
-    text,
+    text as sa_text,
 )
 from sqlalchemy.orm import (
     Mapped,
@@ -1774,7 +1774,7 @@ class ResourceLinkModel(Base):  # type: ignore[misc]
         Text,
         nullable=False,
         default="contains",
-        server_default=text("'contains'"),
+        server_default=sa_text("'contains'"),
     )
 
     # Timestamp (ISO-8601 string)
@@ -2843,8 +2843,8 @@ class DecisionModel(Base):  # type: ignore[misc]
         Index(
             "idx_decisions_superseded",
             "superseded_by",
-            postgresql_where=text("superseded_by IS NOT NULL"),
-            sqlite_where=text("superseded_by IS NOT NULL"),
+            postgresql_where=sa_text("superseded_by IS NOT NULL"),
+            sqlite_where=sa_text("superseded_by IS NOT NULL"),
         ),
     )
 
@@ -3270,7 +3270,7 @@ class CorrectionAttemptModel(Base):  # type: ignore[misc]
     created_at = Column(
         String(30),
         nullable=False,
-        server_default=text("(strftime('%Y-%m-%dT%H:%M:%f', 'now'))"),
+        server_default=sa_text("(strftime('%Y-%m-%dT%H:%M:%f', 'now'))"),
     )
     completed_at = Column(String(30), nullable=True)
 
@@ -3428,11 +3428,11 @@ class InvariantModel(Base):  # type: ignore[misc]
     source_name = Column(String(255), nullable=False)
 
     # Soft-delete flag (active vs archived)
-    active = Column(Boolean, nullable=False, default=True, server_default=text("1"))
+    active = Column(Boolean, nullable=False, default=True, server_default=sa_text("1"))
 
     # Whether this invariant cannot be overridden by project-level invariants
     non_overridable = Column(
-        Boolean, nullable=False, default=False, server_default=text("0"),
+        Boolean, nullable=False, default=False, server_default=sa_text("0"),
     )
 
     # Timestamp (ISO-8601 string)