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/instagram.py

@@ -0,0 +1,114 @@
+"""Best-effort retrieval of an Instagram post caption without login.
+
+Instagram has no login-free API for captions any more (the official oEmbed endpoint needs a
+Meta app and no longer returns post content). We make a single, honest request to the
+public embed page of the post and read the caption from it. Instagram frequently serves an
+empty app shell to servers instead – then the caller falls back to "paste the caption" or
+"import a screenshot". No login, no cookies, no evasion of bot detection.
+"""
+
+import re
+from html.parser import HTMLParser
+from urllib.parse import urlsplit
+
+from .fetch import FetchError, fetch
+from .schema_org import parse_page
+
+HOSTS = {"instagram.com", "www.instagram.com", "m.instagram.com", "instagr.am", "www.instagr.am"}
+_PATH_RE = re.compile(r"^/(?:[\w.]+/)?(?:p|reel|reels|tv)/([A-Za-z0-9_-]{5,40})(?:/|$)")
+_OG_CAPTION_RE = re.compile(r':\s*["“](.+)["”]\s*\.?\s*$', re.DOTALL)
+
+
+class InstagramUnavailable(Exception):
+    pass
+
+
+def shortcode(url):
+    """Shortcode of a post/reel URL, or None if the URL is not an Instagram post."""
+    try:
+        parts = urlsplit(url.strip())
+    except ValueError:
+        return None
+    if (parts.hostname or "").lower() not in HOSTS:
+        return None
+    match = _PATH_RE.match(parts.path)
+    return match.group(1) if match else None
+
+
+def is_instagram(url):
+    return (urlsplit(url.strip()).hostname or "").lower() in HOSTS
+
+
+class _EmbedCaptionParser(HTMLParser):
+    """Reads <div class="Caption"> of the embed page, without username and comment links."""
+
+    def __init__(self):
+        super().__init__(convert_charrefs=True)
+        self.depth = 0  # >0 while inside the caption div
+        self.skip_depth = 0
+        self.parts = []
+        self.image = ""
+
+    def handle_starttag(self, tag, attrs):
+        attrs = dict(attrs)
+        classes = (attrs.get("class") or "").split()
+        if tag == "img" and "EmbeddedMediaImage" in classes and not self.image:
+            self.image = attrs.get("src", "")
+        if self.depth:
+            if tag == "br":
+                self.parts.append("\n")
+                return
+            if self.skip_depth or "CaptionUsername" in classes or "CaptionComments" in classes:
+                self.skip_depth += 1
+            if tag == "div":
+                self.depth += 1
+        elif tag == "div" and "Caption" in classes:
+            self.depth = 1
+
+    def handle_endtag(self, tag):
+        if not self.depth:
+            return
+        if self.skip_depth:
+            self.skip_depth -= 1
+        if tag == "div":
+            self.depth -= 1
+
+    def handle_data(self, data):
+        if self.depth and not self.skip_depth:
+            self.parts.append(data)
+
+    def caption(self):
+        text = "".join(self.parts)
+        text = re.sub(r"[ \t]+", " ", text)
+        return re.sub(r"\n{3,}", "\n\n", text).strip()
+
+
+def parse_embed(page_html):
+    """Return (caption, image_url) from an embed page; caption may be empty."""
+    parser = _EmbedCaptionParser()
+    try:
+        parser.feed(page_html)
+    except Exception:
+        return "", ""
+    caption = parser.caption()
+    image = parser.image
+    if not caption:
+        meta = parse_page(page_html).meta
+        match = _OG_CAPTION_RE.search(meta.get("og:description", "") or meta.get("og:title", ""))
+        caption = match.group(1).strip() if match else ""
+        image = image or meta.get("og:image", "")
+    return caption, image
+
+
+def fetch_caption(code):
+    """Try to read the caption of a post. Raises InstagramUnavailable if Instagram doesn't deliver it."""
+    try:
+        result = fetch(f"https://www.instagram.com/p/{code}/embed/captioned/")
+    except FetchError as error:
+        raise InstagramUnavailable(error.user_message) from None
+    if result.status != 200:
+        raise InstagramUnavailable(f"Instagram antwortete mit Status {result.status}.")
+    caption, image = parse_embed(result.text)
+    if len(caption) < 20:
+        raise InstagramUnavailable("Instagram hat die Beschreibung nicht herausgegeben.")
+    return caption, image