perf+calitate sugestii k-NN: matvec numpy, vot top-5 cu prag calibrat, indicatori import

- embeddings: corpus ca matrice numpy cu norme precalculate; suggest_nearest
  = un matvec (~0.6ms/query fata de ~500ms cosine pur-Python la 17k vectori)
- enrich_suggestions: vot ponderat cu similaritatea pe top-5 vecini (NUL =
  eticheta proprie); prag 0.5 -> 0.88, calibrat LOO pe corpusul SILVER
  (tools/mapare-llm/knn_calibrate.py): precizie 90.5% -> 93.1%, cod gresit
  preselectat 7.2% -> 4.7%; sub prag abtinere -> preselectie fuzzy
- UI: codul sugerat de sistem afisat explicit cu sursa si scorul, separat de
  lista fuzzy ("potrivire text"); indicator de progres reparat pe upload
  (display:inline anula .htmx-indicator) si adaugat pe pasii 2->3 si
  "Salveaza maparile"

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/web/templates/_mapcoloane.html

@@ -65,7 +65,8 @@
 
     <form hx-post="/_import/{{ import_id }}/mapare-coloane"
           hx-target="#import-section"
-          hx-swap="outerHTML">
+          hx-swap="outerHTML"
+          hx-indicator="#mapcol-spinner">
       <input type="hidden" name="csrf_token" value="{{ csrf_token or '' }}">
 
       <div style="margin-bottom:8px; display:flex; align-items:center; gap:10px; flex-wrap:wrap;">
@@ -162,6 +163,11 @@
                 style="min-height:44px; padding:10px 24px; font-size:var(--fs-md);{% if not prima_inreg %} opacity:0.5; cursor:not-allowed;{% endif %}">
           Salveaza si continua la preview
         </button>
+        <span id="mapcol-spinner" class="htmx-indicator muted"
+              style="font-size:var(--fs-sm);" role="status">
+          <span class="spin-dot" aria-hidden="true"></span>
+          se verifica randurile si se calculeaza sugestiile...
+        </span>
         {% if not prima_inreg %}
         <span style="font-size:var(--fs-xs); color:var(--err);">
           Fisierul nu contine randuri de date — incarca un fisier cu cel putin o inregistrare.