Add phase 5: link import, Instagram fallback and share target

- SSRF-safe fetcher: public IPs only, connects to the checked address,
  redirects re-validated, size/time limits, honest user agent
- schema.org/Recipe JSON-LD extraction (graphs, HowToSections, ISO
  durations, yields, keywords, images) without extra dependencies;
  AI fallback on plain page text when no structured recipe exists
- Instagram: one login-free request to the public embed page; when
  Instagram withholds the caption, the import page explains how to paste
  the text or import a screenshot instead
- Suggested source photo can be downloaded and attached on save
- Text import works without AI (text becomes the description)
- Installable PWA with manifest, icons and Android share target
- Offline tests for SSRF rules, parsers, Instagram and import views

Co-Authored-By: Claude Opus 5.5 <[email protected]>

recipes/urls.py

@@ -10,6 +10,8 @@ urlpatterns = [
     path("rezepte/import/", import_views.import_start, name="import"),
     path("rezepte/import/foto/", import_views.import_photo, name="import_photo"),
     path("rezepte/import/text/", import_views.import_text, name="import_text"),
+    path("rezepte/import/link/", import_views.import_link, name="import_link"),
+    path("teilen/", import_views.share_target, name="share"),
     path("rezepte/<int:pk>/", views.recipe_detail, name="detail"),
     path("rezepte/<int:pk>/bearbeiten/", views.recipe_edit, name="edit"),
     path("rezepte/<int:pk>/loeschen/", views.recipe_delete, name="delete"),