feat: comprehensive test infrastructure improvements

- Fix unit test imports: add env setup in conftest.py before module imports
- Add 24 new auth router tests (RBAC, preferences, password validation)
- Add 16 new tests for litellm and chat_summary routers
- Apply black formatting and ruff linting across codebase
- Add pre-commit hooks configuration (black, ruff, file checks)
- Increase CI coverage threshold from 40% to 50%

Test Results:
- 206 tests passing (91 unit + 115 integration)
- Coverage: 58.79% on core modules
- auth.py: 57% → 85%, litellm.py: 23% → 87%, chat_summary.py: 41% → 100%
- auth_service: 96.51%, config: 100%, rbac: 93.48%

dashboard/backend/routers/opc_projects.py

@@ -1,27 +1,29 @@
 """
 OPC Projects and Invoicing Router
 """
-from fastapi import APIRouter, Depends, HTTPException, Response, Request
-from typing import Optional
+
+from datetime import datetime
+
+from fastapi import APIRouter, HTTPException, Request, Response
 from pydantic import BaseModel
+
 from db import opc_db
 from rbac import User
 from services import pdf_service
-from datetime import datetime
 
 router = APIRouter()
 
 
 class ProjectCreate(BaseModel):
     name: str
-    description: Optional[str] = None
-    client_id: Optional[int] = None
+    description: str | None = None
+    client_id: int | None = None
 
 
 class InvoiceGenerate(BaseModel):
     project_id: int
     client_id: int
-    invoice_number: Optional[str] = None
+    invoice_number: str | None = None
 
 
 @router.get("/projects")
@@ -45,11 +47,16 @@ async def create_project(
     user: User = request.state.user
     pool = await opc_db.get_pool()
     async with pool.acquire() as conn:
-        row = await conn.fetchrow("""
+        row = await conn.fetchrow(
+            """
             INSERT INTO projects (name, description, client_id)
             VALUES ($1, $2, $3)
             RETURNING *
-        """, project.name, project.description, project.client_id)
+        """,
+            project.name,
+            project.description,
+            project.client_id,
+        )
         return dict(row)
 
 
@@ -69,18 +76,23 @@ async def list_clients(
 async def create_client(
     request: Request,
     name: str,
-    email: Optional[str] = None,
-    company: Optional[str] = None,
+    email: str | None = None,
+    company: str | None = None,
 ):
     """Create a new client"""
     user: User = request.state.user
     pool = await opc_db.get_pool()
     async with pool.acquire() as conn:
-        row = await conn.fetchrow("""
+        row = await conn.fetchrow(
+            """
             INSERT INTO clients (name, email, company)
             VALUES ($1, $2, $3)
             RETURNING *
-        """, name, email, company)
+        """,
+            name,
+            email,
+            company,
+        )
         return dict(row)
 
 
@@ -100,11 +112,14 @@ async def generate_invoice(
         client = dict(client_row)
 
         # Get time entries for project
-        time_rows = await conn.fetch("""
+        time_rows = await conn.fetch(
+            """
             SELECT * FROM time_entries
             WHERE project_id = $1 AND billable = TRUE
             ORDER BY started_at
-        """, invoice.project_id)
+        """,
+            invoice.project_id,
+        )
 
         if not time_rows:
             raise HTTPException(status_code=400, detail="No billable time entries found")
@@ -116,7 +131,7 @@ async def generate_invoice(
             project_id=invoice.project_id,
             client=client,
             time_entries=time_entries,
-            invoice_number=invoice.invoice_number
+            invoice_number=invoice.invoice_number,
         )
 
         # Return PDF
@@ -124,9 +139,7 @@ async def generate_invoice(
         return Response(
             content=pdf_bytes,
             media_type="application/pdf",
-            headers={
-                "Content-Disposition": f"attachment; filename={filename}"
-            }
+            headers={"Content-Disposition": f"attachment; filename={filename}"},
         )
 
 
@@ -146,5 +159,5 @@ async def get_project_time(
         "total_minutes": total_minutes,
         "total_hours": round(total_minutes / 60, 2),
         "billable_minutes": billable_minutes,
-        "billable_hours": round(billable_minutes / 60, 2)
+        "billable_hours": round(billable_minutes / 60, 2),
     }