feat(5.12): modal editare + cont obligatoriu la import; design.md + PRD 5.13 revizuit (/autoplan)

5.12 (livrat): editare in modal a randurilor de preview, cont obligatoriu inainte de
import, formular editare extras (_form_editare, _editare_preview_modal), plus suita de
teste aferenta (preview edit/compact, mapare op, form editare, signup, admin panel).

Design + planificare:
- docs/design.md: sistem de design (tokeni, breakpoints, scara control, componente, a11y).
- docs/prd/prd-5.12-* si prd-5.13-* (5.13 cu raport /autoplan: CEO+Design+Eng, audit trail).

Curatare: sterse PNG-urile de test/mockup temporare din radacina.

Nota: implementarea CSS 5.13 (responsive compact + sistem butoane) NU e inca facuta —
planul revizuit cere refactorul testelor fragile din test_web_responsive.py INAINTE de CSS.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_admin_lifecycle.py

@@ -36,8 +36,10 @@ def _csrf(client, url="/admin"):
 
 
 def _signup(client, name, email, password="parola_test_001"):
+    from tests.conftest import make_test_cui
     tok = _csrf(client, "/signup")
-    resp = client.post("/signup", data={"name": name, "email": email, "parola": password,
+    resp = client.post("/signup", data={"name": name, "cui": make_test_cui(email),
+                                        "email": email, "parola": password,
                                         "csrf_token": tok}, follow_redirects=True)
     assert resp.status_code == 200
     from app.db import get_connection