feat: Initialize FastAPI application with Azure authentication and transaction management

- Added .env.example for environment variable configuration.
- Created app initialization files and core settings management.
- Implemented API routers for reporting and transaction endpoints.
- Developed transaction management service with CRUD operations.
- Integrated Azure OAuth for user authentication.
- Designed dashboard view with transaction filtering and display.
- Added Swagger UI documentation with custom dark theme.
- Created static and template files for frontend styling and layout.

app/api/__init__.py

@@ -0,0 +1,4 @@
+from app.api.reporting import router as reporting_router
+from app.api.transactions import router as transactions_router
+
+__all__ = ["reporting_router", "transactions_router"]

app/api/reporting.py

@@ -0,0 +1,11 @@
+from fastapi import APIRouter
+
+from app.service.models import ReconSummary
+from app.service.recon_service import get_summary
+
+router = APIRouter(prefix="/api", tags=["Reporting"])
+
+
+@router.get("/summary", response_model=ReconSummary, summary="Reconciliation summary")
+async def get_summary_endpoint() -> ReconSummary:
+    return get_summary()

app/api/transactions.py

@@ -0,0 +1,44 @@
+from fastapi import APIRouter, HTTPException, Query
+
+from app.service.models import Transaction
+from app.service.recon_service import (
+    FlagType,
+    StatusType,
+    add_transaction,
+    delete_transaction_by_id,
+    get_transaction_by_id,
+    list_transactions,
+)
+
+router = APIRouter(prefix="/api", tags=["Transactions"])
+
+
+@router.get("/transactions", response_model=list[Transaction], summary="List transactions")
+async def list_transactions_endpoint(
+    status: StatusType | None = Query(None, description="Filter by status"),
+    flag: FlagType | None = Query(None, description="Filter by flag"),
+) -> list[Transaction]:
+    return list_transactions(status=status, flag=flag)
+
+
+@router.get("/transactions/{transaction_id}", response_model=Transaction, summary="Get a transaction")
+async def get_transaction_endpoint(transaction_id: str) -> Transaction:
+    transaction = get_transaction_by_id(transaction_id)
+    if transaction is None:
+        raise HTTPException(status_code=404, detail=f"{transaction_id} not found")
+    return transaction
+
+
+@router.post("/transactions", response_model=Transaction, status_code=201, summary="Submit a transaction")
+async def create_transaction_endpoint(transaction: Transaction) -> Transaction:
+    created = add_transaction(transaction)
+    if not created:
+        raise HTTPException(status_code=409, detail=f"{transaction.transaction_id} already exists")
+    return transaction
+
+
+@router.delete("/transactions/{transaction_id}", status_code=204, summary="Delete a transaction")
+async def delete_transaction_endpoint(transaction_id: str) -> None:
+    removed = delete_transaction_by_id(transaction_id)
+    if not removed:
+        raise HTTPException(status_code=404, detail=f"{transaction_id} not found")