feat(case): add GET /case/{id} detail view and Jinja template; link from dashboard table; eager-load related data; 404 handling and logging

app/main.py

@@ -15,7 +15,7 @@ from starlette.middleware.sessions import SessionMiddleware
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
-from sqlalchemy.orm import Session
+from sqlalchemy.orm import Session, joinedload
 from sqlalchemy import or_
 from dotenv import load_dotenv
 from starlette.middleware.base import BaseHTTPMiddleware
@@ -314,3 +314,58 @@ async def admin_panel(request: Request, db: Session = Depends(get_db)):
         "request": request,
         "user": user
     })
+
+
+@app.get("/case/{case_id}")
+async def case_detail(
+    request: Request,
+    case_id: int,
+    db: Session = Depends(get_db),
+):
+    """
+    Case detail view.
+
+    Displays detailed information for a single case and its related client and
+    associated records (transactions, documents, payments).
+    """
+    # Check authentication
+    user = get_current_user_from_session(request.session)
+    if not user:
+        return RedirectResponse(url="/login", status_code=302)
+
+    # Fetch case with related entities eagerly loaded to avoid lazy-load issues
+    case_obj = (
+        db.query(Case)
+        .options(
+            joinedload(Case.client),
+            joinedload(Case.transactions),
+            joinedload(Case.documents),
+            joinedload(Case.payments),
+        )
+        .filter(Case.id == case_id)
+        .first()
+    )
+
+    if not case_obj:
+        logger.warning("Case not found: id=%s", case_id)
+        return templates.TemplateResponse(
+            "case.html",
+            {
+                "request": request,
+                "user": user,
+                "case": None,
+                "error": "Case not found",
+            },
+            status_code=404,
+        )
+
+    logger.info("Rendering case detail: id=%s, file_no='%s'", case_obj.id, case_obj.file_no)
+
+    return templates.TemplateResponse(
+        "case.html",
+        {
+            "request": request,
+            "user": user,
+            "case": case_obj,
+        },
+    )