feat(5.18): VERIFY+CLOSE — US-007 badge sursa + fix findings code-review

VERIFY PASS pe corpus k-NN exemple etichetate (seed real 17181 Haiku, comis
in 756f777): suita 1392 passed, 1 deselected (live); smoke init_db seeder
(17181/NUL=2200/idempotent); toate codurile in nomenclator.

US-007 (cerere user la CLOSE) — badge sursa pe sugestia fuzzy din editor:
- _mapari.html: chip confirmat (GOLD) / similar (SILVER+k-NN) / non-operatie (NUL)
- base.html: .sugg-sursa--{confirmat,similar,nul} pe tokeni de tema (color-mix)
- routes.py: cheia `nul` adaugata in surse_sugestie default (finding cross-file)
- tests/test_web_badge_sursa.py: gold/silver/nul/fara-sursa (4 teste)
- E2E render live verificat in serverul real (/_fragments/mapari)

CLOSE /code-review high (main..HEAD, 3 finder x 8 unghiuri) — runtime curat,
invariant #13 intact; 3 findings low/cosmetic REPARATE + lock-uite:
- shared_store.seed_suggestions: cod whitespace -> NULL (era ''), + test lock
- genereaza_seed.py: with open(...) in loc de open().read() (FD leak tool offline)
- embeddings.py: docstring-uri aliniate la [{cod, is_nul, similaritate}]

ROADMAP: 5.18 LIVRAT. PRD: raport VERIFY/CLOSE scris.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_shared_store.py

@@ -141,6 +141,21 @@ def test_seed_suggestions_nul_cu_cod_explicit_tot_nul(conn):
     assert row["cod_prestatie"] is None  # cod explicit ignorat cand is_nul
 
 
+def test_seed_suggestions_cod_whitespace_devine_null(conn):
+    """Rand non-NUL cu cod whitespace-only ('   ') -> cod_prestatie NULL, NU '' (corectitudine)."""
+    from app.shared_store import seed_suggestions, lookup_suggestion
+
+    seed_suggestions(conn, [
+        {"denumire": "OPERATIE CU COD GOL", "cod_prestatie": "   ", "source": "llm", "confidence": 0.5},
+    ])
+    conn.commit()
+
+    row = lookup_suggestion(conn, "OPERATIE CU COD GOL")
+    assert row is not None
+    assert row["is_nul"] == 0  # nu e marcat NUL
+    assert row["cod_prestatie"] is None  # whitespace -> NULL, nu '' (rand non-NUL fara cod gol)
+
+
 def test_seed_suggestions_normalizare_diacritice(conn):
     """Lookup pe forma cu diacritice gaseste randul seedat fara diacritice (normalize_for_match)."""
     from app.shared_store import seed_suggestions, lookup_suggestion