ui: restyle login, dedupe navbar with Jinja macros, touch polish

- login: theme variables instead of hardcoded slate colors, decorative
  brand background, show/hide password toggle, dynamic copyright year
- navbar: nav links rendered via shared nav_link/nav_links macros
  (desktop + mobile from one source), active state now also in mobile
  menu, aria-current on active link, fix nonexistent w-4.5 class
- themes.css: btn :active press feedback, btn-lg variant, card hover
  border accent, brand accent-color and ::selection
- fix tmf-input vs pl-10 cascade conflict (themes.css loads after
  tailwind.css) with important utilities — also fixes recipe search icon
- app.py: inject current_year in template globals
- i18n: add Mostra/Nascondi password (IT/EN)

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

src/frontend/flask_app/templates/maker/recipe_list.html

@@ -120,7 +120,7 @@
             </div>
             <input type="text"
                    x-model="search"
-                   class="tmf-input pl-10"
+                   class="tmf-input !pl-10"
                    :placeholder="'{{ _('Cerca per nome, codice o descrizione...') }}'">
           </div>
         </div>