Add tree organization system with categories, tags, and folders

Features:
- Categories: Global and team-specific tree categorization (admin-managed)
- Tags: Flexible tree tagging with autocomplete (author + admin)
- User folders: Personal tree collections with subfolder support
  - Hierarchical structure (max 3 levels deep)
  - Right-click context menu for folder management
  - Cascade delete for subfolders
- Filter trees by category, tags, and folder in library view

Backend:
- New models: Category, Tag, UserFolder with relationships
- New API endpoints for categories, tags, and folders
- Tree organization migrations (005, 006)

Frontend:
- FolderSidebar with hierarchical folder tree
- FolderEditModal for create/edit with color picker
- AddToFolderMenu for quick tree organization
- TagInput with autocomplete and TagBadges display
- Updated TreeMetadataForm and TreeLibraryPage

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/schemas/tree.py

@@ -4,9 +4,20 @@ from uuid import UUID
 from pydantic import BaseModel, Field
 
 
+class CategoryInfo(BaseModel):
+    """Embedded category info for tree responses."""
+    id: UUID
+    name: str
+    slug: str
+
+    class Config:
+        from_attributes = True
+
+
 class TreeBase(BaseModel):
     name: str = Field(..., min_length=1, max_length=255)
     description: Optional[str] = None
+    # Legacy category field - kept for backward compatibility
     category: Optional[str] = Field(None, max_length=100)
 
 
@@ -14,15 +25,19 @@ class TreeCreate(TreeBase):
     tree_structure: dict[str, Any] = Field(..., description="The decision tree structure in JSON format")
     is_public: bool = Field(False, description="Make tree visible to all users")
     is_default: bool = Field(False, description="Mark as a default/system tree (admin only)")
+    category_id: Optional[UUID] = Field(None, description="Category ID from tree_categories table")
+    tags: Optional[list[str]] = Field(None, max_length=10, description="List of tag names to assign")
 
 
 class TreeUpdate(BaseModel):
     name: Optional[str] = Field(None, min_length=1, max_length=255)
     description: Optional[str] = None
     category: Optional[str] = Field(None, max_length=100)
+    category_id: Optional[UUID] = None
     tree_structure: Optional[dict[str, Any]] = None
     is_public: Optional[bool] = None
     is_active: Optional[bool] = None
+    tags: Optional[list[str]] = Field(None, max_length=10, description="List of tag names to assign (replaces existing)")
 
 
 class TreeResponse(TreeBase):
@@ -30,6 +45,9 @@ class TreeResponse(TreeBase):
     tree_structure: dict[str, Any]
     author_id: Optional[UUID] = None
     team_id: Optional[UUID] = None
+    category_id: Optional[UUID] = None
+    category_info: Optional[CategoryInfo] = None
+    tags: list[str] = []  # List of tag names
     is_active: bool
     is_public: bool
     is_default: bool
@@ -47,6 +65,10 @@ class TreeListResponse(BaseModel):
     name: str
     description: Optional[str] = None
     category: Optional[str] = None
+    category_id: Optional[UUID] = None
+    category_info: Optional[CategoryInfo] = None
+    tags: list[str] = []  # List of tag names
+    author_id: Optional[UUID] = None
     is_active: bool
     is_public: bool
     is_default: bool