fix: harden habit input and lifecycle

backend/schemas.py

@@ -1,7 +1,7 @@
 from datetime import datetime
 from uuid import UUID
 
-from pydantic import BaseModel, ConfigDict, Field, model_validator
+from pydantic import BaseModel, ConfigDict, Field, field_validator, model_validator
 
 
 class InitializeRequest(BaseModel):
@@ -45,6 +45,14 @@ class SessionOut(BaseModel):
 class NameUpdate(BaseModel):
     name: str = Field(min_length=1, max_length=120)
 
+    @field_validator("name")
+    @classmethod
+    def clean_name(cls, value):
+        value = value.strip()
+        if not value:
+            raise ValueError("name cannot be blank")
+        return value
+
 
 class FolderCreate(NameUpdate):
     pass
@@ -56,8 +64,7 @@ class FolderOut(BaseModel):
     name: str
 
 
-class ListCreate(BaseModel):
-    name: str = Field(min_length=1, max_length=120)
+class ListCreate(NameUpdate):
     folder_id: UUID | None = None
 
 
@@ -80,6 +87,14 @@ class TaskCreate(BaseModel):
     parent_id: UUID | None = None
     rrule: str | None = Field(default=None, min_length=5, max_length=1000)
 
+    @field_validator("title")
+    @classmethod
+    def clean_title(cls, value):
+        value = value.strip()
+        if not value:
+            raise ValueError("title cannot be blank")
+        return value
+
 
 class TaskUpdate(BaseModel):
     title: str | None = Field(default=None, min_length=1, max_length=500)
@@ -91,6 +106,16 @@ class TaskUpdate(BaseModel):
     list_id: UUID | None = None
     version: int = Field(ge=1)
 
+    @field_validator("title")
+    @classmethod
+    def clean_title(cls, value):
+        if value is None:
+            return value
+        value = value.strip()
+        if not value:
+            raise ValueError("title cannot be blank")
+        return value
+
     @model_validator(mode="after")
     def reject_null_non_nullable_fields(self):
         for field in ("title", "description", "priority", "completed", "list_id", "due_has_time"):