feat: add slug-only dashboard profile filter and unify backend imports

backend/src/schemas/profile.py

@@ -45,6 +45,7 @@ class ProfilePreference(BaseModel):
     superset_username: Optional[str] = None
     superset_username_normalized: Optional[str] = None
     show_only_my_dashboards: bool = False
+    show_only_slug_dashboards: bool = True
 
     git_username: Optional[str] = None
     git_email: Optional[str] = None
@@ -79,6 +80,10 @@ class ProfilePreferenceUpdateRequest(BaseModel):
         default=None,
         description='When true, "/dashboards" can auto-apply profile filter in main context.',
     )
+    show_only_slug_dashboards: Optional[bool] = Field(
+        default=None,
+        description='When true, "/dashboards" hides dashboards without slug by default.',
+    )
     git_username: Optional[str] = Field(
         default=None,
         description="Git author username used for commit signature.",
@@ -172,4 +177,4 @@ class SupersetAccountLookupResponse(BaseModel):
     items: List[SupersetAccountCandidate] = Field(default_factory=list)
 # [/DEF:SupersetAccountLookupResponse:Class]
 
-# [/DEF:backend.src.schemas.profile:Module]
+# [/DEF:backend.src.schemas.profile:Module]