M6 1901: URL capture with link-preview unfurl (SSRF-hardened)

Paste a link → fetch its OpenGraph/meta preview (title, description, image,
site) and show a rich card. User-triggered + persisted (never auto-fetches;
cached so it never re-fetches). Opt-in via a new admin setting
enable_url_unfurl (default on, rule 26).

Security (the whole point of this task): a new dependency-free unfurl.py
does the fetch with layered SSRF defenses — http/https only; resolve the
host and reject EVERY non-public address (private/loopback/link-local/
reserved/multicast/unspecified — blocks 169.254.169.254 etc.); connect to
the vetted IP with SNI so DNS-rebinding can't slip through; ≤3 redirects
each re-validated; 5s timeout; 512 KB cap; text/html only; blocking IO in a
worker thread. No server-side image fetch — the og:image URL is loaded by
the browser.

- note_link_previews table (migration 0020), one per (note, url); serialized
  inline on notes (+ rides the sync pull feed read-only).
- POST /api/notes/<id>/unfurl {url} (owner-scoped, setting-gated, 502 on
  fetch failure); DELETE /api/notes/<id>/previews/<id>.
- enable_url_unfurl exposed in public config so the UI hides the affordance
  when disabled.

Frontend: LinkPreview.vue card; editor detects URLs in the body and offers a
"Preview <domain>" chip per un-previewed link (ensureDraft first), renders
preview cards with remove; card shows previews read-only. New link icon;
notes-store unfurl()/deletePreview().

Tests (DB-free): is_public_ip range blocking, validate_url scheme/parts,
extract_preview (OG + <title> fallback + relative-image resolve), endpoint
auth-guards.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/stores/notes.ts

@@ -32,6 +32,16 @@ export interface Attachment {
   sha256?: string | null;
 }
 
+// A cached OpenGraph/meta preview for a URL in the note (server-fetched, SSRF-guarded).
+export interface LinkPreview {
+  id: string;
+  url: string;
+  title: string | null;
+  description: string | null;
+  image_url: string | null;
+  site_name: string | null;
+}
+
 // A past version of a note's title+body (version history).
 export interface NoteRevision {
   id: string;
@@ -57,6 +67,7 @@ export interface Note {
   labels: NoteLabel[];
   items: ChecklistItem[];
   attachments: Attachment[];
+  previews: LinkPreview[];
   created_at: string | null;
   updated_at: string | null;
 }
@@ -174,6 +185,14 @@ export const useNotesStore = defineStore("notes", () => {
     reconcile(await api.del<Note>(`/api/notes/${id}/attachments/${attId}`));
   }
 
+  async function unfurl(id: string, url: string): Promise<void> {
+    reconcile(await api.post<Note>(`/api/notes/${id}/unfurl`, { url }));
+  }
+
+  async function deletePreview(id: string, previewId: string): Promise<void> {
+    reconcile(await api.del<Note>(`/api/notes/${id}/previews/${previewId}`));
+  }
+
   async function importNotes(file: File): Promise<{ source: string; imported: number; skipped: number }> {
     const form = new FormData();
     form.append("file", file);
@@ -262,6 +281,8 @@ export const useNotesStore = defineStore("notes", () => {
     deleteItem,
     uploadAttachment,
     deleteAttachment,
+    unfurl,
+    deletePreview,
     importNotes,
     fetchOne,
     createTitled,