Initial commit: Backend API Phase 1a complete

- FastAPI backend with JWT auth
- PostgreSQL database schema
- Trees and Sessions CRUD APIs
- Export functionality (Markdown, Text, HTML)
- Docker setup for local development
- Alembic migrations

backend/app/schemas/session.py

@@ -0,0 +1,51 @@
+from datetime import datetime
+from typing import Optional, Any
+from uuid import UUID
+from pydantic import BaseModel, Field
+
+
+class DecisionRecord(BaseModel):
+    node_id: str
+    question: Optional[str] = None
+    answer: Optional[str] = None
+    action_performed: Optional[str] = None
+    notes: Optional[str] = None
+    automation_used: Optional[bool] = False
+    timestamp: datetime
+    attachments: list[str] = Field(default_factory=list)
+
+
+class SessionCreate(BaseModel):
+    tree_id: UUID
+    ticket_number: Optional[str] = Field(None, max_length=100)
+    client_name: Optional[str] = Field(None, max_length=255)
+
+
+class SessionUpdate(BaseModel):
+    path_taken: Optional[list[str]] = None
+    decisions: Optional[list[DecisionRecord]] = None
+    ticket_number: Optional[str] = Field(None, max_length=100)
+    client_name: Optional[str] = Field(None, max_length=255)
+
+
+class SessionResponse(BaseModel):
+    id: UUID
+    tree_id: UUID
+    user_id: UUID
+    tree_snapshot: dict[str, Any]
+    path_taken: list[str]
+    decisions: list[dict[str, Any]]
+    started_at: datetime
+    completed_at: Optional[datetime] = None
+    ticket_number: Optional[str] = None
+    client_name: Optional[str] = None
+    exported: bool
+
+    class Config:
+        from_attributes = True
+
+
+class SessionExport(BaseModel):
+    format: str = Field(default="markdown", pattern="^(text|markdown|html)$")
+    include_timestamps: bool = True
+    include_tree_info: bool = True