fix(web): stop presenting an unscored case as a failed analysis, and four smaller things

From clicking through the redesigned UI:

- scoring a case without a model registry painted a red failure across a case that had in
  fact analysed fine. It is now a quiet note saying the model term contributes 0, because
  scoring is an optional fourth of the rank, not the analysis.
- the MLflow default moves to port 5001. On macOS, AirPlay Receiver owns 5000, which is why
  the registry answered "403" rather than refusing the connection; docker-compose publishes
  5001 to match.
- a funnel step that kept nothing drew a visible bar. Zero now draws zero.
- "1 candidates".
- the funnel's fixed grid columns forced a horizontal scrollbar on the report.

The report also lists the top undecided candidates now: the first thing anyone opens has no
decisions in it, and "Shortlisted (0)" alone said nothing about what the tool found.

Tests: api 77, web 32; ruff, mypy, svelte-check clean.

api/app/routers/cases.py

@@ -36,6 +36,8 @@ from app.services.scoring import score_job
 logger = logging.getLogger(__name__)
 router = APIRouter()
 
+REPORT_TOP = 5
+
 
 async def _case_or_404(session: SessionDep, case_id: uuid.UUID) -> Case:
     case = await case_view.get_case(session, case_id)
@@ -208,6 +210,11 @@ async def report(case_id: uuid.UUID, session: SessionDep) -> ReportOut:
         ]
 
     shortlisted, dismissed = decided(DecisionState.shortlisted), decided(DecisionState.dismissed)
+    top = [
+        CandidateOut.from_candidate(c, labels)
+        for c in view.candidates
+        if c.variant.decision is None
+    ][:REPORT_TOP]
     prediction = next((c.variant.prediction for c in view.candidates if c.variant.prediction), None)
     return ReportOut(
         case=_as_case_out(case, view.job, len(shortlisted)),
@@ -222,4 +229,5 @@ async def report(case_id: uuid.UUID, session: SessionDep) -> ReportOut:
         ),
         shortlisted=shortlisted,
         dismissed=dismissed,
+        top=top,
     )