refactor(db): rename search_space to workspace in satellite ORM models (Phase 2 Wave B)

Flip search_space_id -> workspace_id and the workspace relationship/back_populates
in the automations, file_storage, notifications, and podcasts persistence models,
and drop the Phase 1 Column("workspace_id", ...) shim. Full SQLAlchemy mapper
configuration now passes (db.py + satellites consistent).

surfsense_backend/app/automations/persistence/models/automation.py

@@ -24,8 +24,7 @@ from ..enums.automation_status import AutomationStatus
 class Automation(BaseModel, TimestampMixin):
     __tablename__ = "automations"
 
-    search_space_id = Column(
-        "workspace_id",
+    workspace_id = Column(
         Integer,
         ForeignKey("workspaces.id", ondelete="CASCADE"),
         nullable=False,
@@ -66,7 +65,7 @@ class Automation(BaseModel, TimestampMixin):
         index=True,
     )
 
-    search_space = relationship("SearchSpace", back_populates="automations")
+    workspace = relationship("Workspace", back_populates="automations")
     created_by = relationship("User", back_populates="automations")
     triggers = relationship(
         "AutomationTrigger",

surfsense_backend/app/file_storage/persistence/models.py

@@ -29,8 +29,7 @@ class DocumentFile(BaseModel, TimestampMixin):
         nullable=False,
         index=True,
     )
-    search_space_id = Column(
-        "workspace_id",
+    workspace_id = Column(
         Integer,
         ForeignKey("workspaces.id", ondelete="CASCADE"),
         nullable=False,

surfsense_backend/app/notifications/persistence/models.py

@@ -47,8 +47,7 @@ class Notification(BaseModel, TimestampMixin):
         nullable=False,
         index=True,
     )
-    search_space_id = Column(
-        "workspace_id",
+    workspace_id = Column(
         Integer,
         ForeignKey("workspaces.id", ondelete="CASCADE"),
         nullable=True,
@@ -70,4 +69,4 @@ class Notification(BaseModel, TimestampMixin):
     )
 
     user = relationship("User", back_populates="notifications")
-    search_space = relationship("SearchSpace", back_populates="notifications")
+    workspace = relationship("Workspace", back_populates="notifications")

surfsense_backend/app/podcasts/persistence/models.py

@@ -68,13 +68,12 @@ class Podcast(BaseModel, TimestampMixin):
     # Legacy local audio path; retained for back-compat until cutover.
     file_location = Column(Text, nullable=True)
 
-    search_space_id = Column(
-        "workspace_id",
+    workspace_id = Column(
         Integer,
         ForeignKey("workspaces.id", ondelete="CASCADE"),
         nullable=False,
     )
-    search_space = relationship("SearchSpace", back_populates="podcasts")
+    workspace = relationship("Workspace", back_populates="podcasts")
 
     thread_id = Column(
         Integer,