Enhance knowledge base functionality and integrate S3 storage support

- Add new models for `KnowledgeDocument` and `KnowledgeChunk` to manage document ingestion and chunking.
- Implement S3-compatible storage integration for knowledge documents, allowing for file uploads and retrieval.
- Introduce API endpoints for managing knowledge bases and documents, including creation, deletion, and searching.
- Update frontend components to support knowledge base configuration and document management, improving user interaction.
- Enhance backend services for knowledge processing and retrieval, ensuring robust handling of document statuses and errors.

backend/db/models.py

@@ -22,6 +22,7 @@ from sqlalchemy import (
 )
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
+from pgvector.sqlalchemy import Vector
 
 
 class Base(DeclarativeBase):
@@ -93,6 +94,49 @@ class KnowledgeBase(Base):
     )
 
 
+class KnowledgeDocument(Base):
+    """A file or pasted text ingested into one knowledge base."""
+
+    __tablename__ = "knowledge_documents"
+
+    id: Mapped[str] = mapped_column(String(40), primary_key=True)
+    knowledge_base_id: Mapped[str] = mapped_column(
+        String(40), ForeignKey("knowledge_bases.id", ondelete="CASCADE"), index=True
+    )
+    name: Mapped[str] = mapped_column(String(255))
+    source_type: Mapped[str] = mapped_column(String(16))  # file|text
+    mime_type: Mapped[str] = mapped_column(String(128), default="text/plain")
+    storage_key: Mapped[str | None] = mapped_column(String(1024), nullable=True)
+    size_bytes: Mapped[int] = mapped_column(Integer, default=0)
+    status: Mapped[str] = mapped_column(String(16), default="processing")
+    error_message: Mapped[str] = mapped_column(String(2048), default="")
+    chunk_count: Mapped[int] = mapped_column(Integer, default=0)
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
+    )
+
+
+class KnowledgeChunk(Base):
+    """Searchable text chunk; Vector has no fixed dimension to support configured models."""
+
+    __tablename__ = "knowledge_chunks"
+    __table_args__ = (
+        UniqueConstraint("document_id", "chunk_index", name="uq_knowledge_chunk_position"),
+    )
+
+    id: Mapped[str] = mapped_column(String(40), primary_key=True)
+    knowledge_base_id: Mapped[str] = mapped_column(
+        String(40), ForeignKey("knowledge_bases.id", ondelete="CASCADE"), index=True
+    )
+    document_id: Mapped[str] = mapped_column(
+        String(40), ForeignKey("knowledge_documents.id", ondelete="CASCADE"), index=True
+    )
+    chunk_index: Mapped[int] = mapped_column(Integer)
+    content: Mapped[str] = mapped_column(Text)
+    embedding: Mapped[list[float]] = mapped_column(Vector())
+
+
 class Assistant(Base):
     """助手(单表,无版本化)。type 为可变普通列,5 种类型共用此表。