Suggest existing categories/manufacturers when editing

The category and manufacturer fields in the edit form now offer the
already-used values via a datalist dropdown, while still allowing a
new value to be typed. Both edit entry points (open edit form and AI
re-describe) pass the current lists.

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

app/main.py

@@ -358,6 +358,17 @@ def _parse_tags(raw: str) -> list[str]:
     return [t.strip() for t in raw.split(",") if t.strip()][:8]
 
 
+def _edit_context(request: Request, db: Session, user: User, link: Link) -> dict:
+    existing = facets(db, user)
+    return {
+        "request": request,
+        "link": link,
+        "ai_enabled": config.AI_ENABLED,
+        "all_categories": [name for name, _ in existing["categories"]],
+        "all_manufacturers": [name for name, _ in existing["manufacturers"]],
+    }
+
+
 @app.get("/links/{link_id}/edit", response_class=HTMLResponse)
 def edit_link_form(
     link_id: int,
@@ -371,8 +382,7 @@ def edit_link_form(
     if not link:
         return Response(status_code=404)
     return templates.TemplateResponse(
-        "_link_card_edit.html",
-        {"request": request, "link": link, "ai_enabled": config.AI_ENABLED},
+        "_link_card_edit.html", _edit_context(request, db, user, link)
     )
 
 
@@ -469,6 +479,5 @@ def reanalyze_link(
     db.commit()
     db.refresh(link)
     return templates.TemplateResponse(
-        "_link_card_edit.html",
-        {"request": request, "link": link, "ai_enabled": config.AI_ENABLED},
+        "_link_card_edit.html", _edit_context(request, db, user, link)
     )