feat(5.9): US-006 - fundatie responsive (viewport, nav, modal full-screen mobil)

- base.html: conventie breakpoint unic 767px documentata + bloc @media mobil extins
- modal full-screen pe mobil (100vw/100vh, fara backdrop lateral, x >=44px, scroll intern)
- header/nav colapsat sub 768px + tinte touch >=44px (.icon-btn/.tab-link/.cont-menu)
- tests/test_web_responsive.py NOU (3 teste) + prd.json/progress.txt US-006 passes

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

scripts/ralph/prd.json

@@ -93,12 +93,12 @@
       ],
       "requiresBrowserCheck": true,
       "requiresDesignReview": true,
-      "passes": false,
+      "passes": true,
       "failed": false,
       "blocked": false,
       "retries": 0,
       "failureReason": "",
-      "notes": ""
+      "notes": "Atins: app/web/templates/base.html (conventie breakpoint unic 767px documentata; bloc `@media (max-width:767px)` US-006 extins cu: modal full-screen — overlay fara padding/align-stretch, dialog 100vw/100vh fara border-radius/umbra, modal-close 44x44px, scroll intern; header colapsat flex-wrap + main padding redus; tinte touch >=44px pe .icon-btn/.tab-link/.cont-menu items; comentariu desktop modal actualizat), tests/test_web_responsive.py NOU (3 teste: test_viewport_meta_prezent, test_modal_fullscreen_clasa_mobil, test_nav_colapsabil_sub_breakpoint). meta viewport deja prezent (confirmat, neatins). Nav colapsabil (hamburger cont + tab-bar overflow-x) deja livrat de PRD-uri anterioare; US-006 a adaugat doar tintele touch 44px sub breakpoint. Gates: pytest PASS (fisier 3/3; suita completa 829 passed, 1 deselected — fata de 826 inainte). DEFERAT la VERIFY: requiresBrowserCheck + requiresDesignReview (gstack browser la 375px pe / — fara scroll orizontal, hamburger deschide meniul, modal full-screen + inchidere din x) NErulate in loop fara browser."
     },
     {
       "id": "US-002",