Implement Phase 3: dynamic graph builder, blueprint persistence, and CRUD API

- Add dynamic_graph_builder.py that constructs LangGraph graphs at runtime
  from frontend CouncilBlueprint JSON (no more hardcoded graphs in production)
- Add PostgreSQL persistence via SQLAlchemy async with Blueprint model
- Add blueprint CRUD endpoints (POST/GET/PUT/DELETE /api/councils/)
- Add POST /api/councils/{id}/run to execute blueprints dynamically
- Add Alembic migration infrastructure with initial blueprints table
- Add database.py with async engine and SQLite fallback for dev/test
- Fix missing typing-extensions and add aiosqlite dependency
- Add 42 new tests (80/80 total passing) covering dynamic graph building,
  blueprint service CRUD, and API integration

https://claude.ai/code/session_014yZUxrPsgZbvkebXbCXR4U

backend/api/blueprint_routes.py

@@ -0,0 +1,153 @@
+"""
+REST API routes for council blueprint CRUD.
+
+Endpoints:
+    GET    /api/councils/           — List all blueprints
+    POST   /api/councils/           — Create a new blueprint
+    GET    /api/councils/{id}       — Get a specific blueprint
+    PUT    /api/councils/{id}       — Update a blueprint
+    DELETE /api/councils/{id}       — Delete a blueprint
+"""
+
+from typing import List, Optional
+
+from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel, Field
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from database import get_session
+from services.blueprint_service import (
+    create_blueprint,
+    delete_blueprint,
+    get_blueprint,
+    list_blueprints,
+    update_blueprint,
+)
+
+blueprint_router = APIRouter()
+
+
+# ---------------------------------------------------------------------------
+# Request / Response Models
+# ---------------------------------------------------------------------------
+
+class AgentTools(BaseModel):
+    webSearch: bool = False
+    pdfReader: bool = False
+
+
+class BlueprintNodeSchema(BaseModel):
+    id: str
+    label: str
+    systemPrompt: str = ""
+    model: str = "claude-3-5-sonnet"
+    tools: AgentTools = Field(default_factory=AgentTools)
+    position: dict = Field(default_factory=lambda: {"x": 0, "y": 0})
+
+
+class BlueprintEdgeSchema(BaseModel):
+    id: str
+    source: str
+    target: str
+    type: str = "linear"
+    condition: Optional[str] = None
+
+
+class BlueprintCreateRequest(BaseModel):
+    version: int = 1
+    name: str = Field(..., min_length=1, max_length=255)
+    nodes: List[BlueprintNodeSchema]
+    edges: List[BlueprintEdgeSchema] = []
+    id: Optional[str] = None
+
+
+class BlueprintUpdateRequest(BaseModel):
+    name: Optional[str] = Field(None, min_length=1, max_length=255)
+    nodes: Optional[List[BlueprintNodeSchema]] = None
+    edges: Optional[List[BlueprintEdgeSchema]] = None
+
+
+class BlueprintResponse(BaseModel):
+    id: str
+    version: int
+    name: str
+    nodes: list
+    edges: list
+    createdAt: Optional[str] = None
+    updatedAt: Optional[str] = None
+
+
+# ---------------------------------------------------------------------------
+# Endpoints
+# ---------------------------------------------------------------------------
+
+@blueprint_router.get("/councils/", response_model=List[BlueprintResponse])
+async def list_all_blueprints(
+    session: AsyncSession = Depends(get_session),
+):
+    """List all council blueprints."""
+    blueprints = await list_blueprints(session)
+    return [bp.to_dict() for bp in blueprints]
+
+
+@blueprint_router.post(
+    "/councils/",
+    response_model=BlueprintResponse,
+    status_code=201,
+)
+async def create_new_blueprint(
+    request: BlueprintCreateRequest,
+    session: AsyncSession = Depends(get_session),
+):
+    """Create a new council blueprint."""
+    bp = await create_blueprint(
+        session=session,
+        name=request.name,
+        nodes=[n.model_dump() for n in request.nodes],
+        edges=[e.model_dump() for e in request.edges],
+        blueprint_id=request.id,
+        version=request.version,
+    )
+    return bp.to_dict()
+
+
+@blueprint_router.get("/councils/{blueprint_id}", response_model=BlueprintResponse)
+async def get_single_blueprint(
+    blueprint_id: str,
+    session: AsyncSession = Depends(get_session),
+):
+    """Retrieve a specific blueprint by ID."""
+    bp = await get_blueprint(session, blueprint_id)
+    if bp is None:
+        raise HTTPException(status_code=404, detail=f"Blueprint '{blueprint_id}' not found.")
+    return bp.to_dict()
+
+
+@blueprint_router.put("/councils/{blueprint_id}", response_model=BlueprintResponse)
+async def update_existing_blueprint(
+    blueprint_id: str,
+    request: BlueprintUpdateRequest,
+    session: AsyncSession = Depends(get_session),
+):
+    """Update an existing blueprint."""
+    bp = await update_blueprint(
+        session=session,
+        blueprint_id=blueprint_id,
+        name=request.name,
+        nodes=[n.model_dump() for n in request.nodes] if request.nodes is not None else None,
+        edges=[e.model_dump() for e in request.edges] if request.edges is not None else None,
+    )
+    if bp is None:
+        raise HTTPException(status_code=404, detail=f"Blueprint '{blueprint_id}' not found.")
+    return bp.to_dict()
+
+
+@blueprint_router.delete("/councils/{blueprint_id}", status_code=204)
+async def delete_existing_blueprint(
+    blueprint_id: str,
+    session: AsyncSession = Depends(get_session),
+):
+    """Delete a blueprint by ID."""
+    deleted = await delete_blueprint(session, blueprint_id)
+    if not deleted:
+        raise HTTPException(status_code=404, detail=f"Blueprint '{blueprint_id}' not found.")