feat: autolink URLs in list items, link picker, and inline edit

- Add autolink Jinja2 filter to detect URLs and make them clickable
- Add link picker dropdown to insert existing link URLs into list item content
- Add inline edit with link picker on each list item row
- Apply autolink filter on list detail and focus available list items

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/template_filters.py

@@ -0,0 +1,49 @@
+"""Jinja2 custom template filters."""
+
+import re
+from markupsafe import Markup, escape
+
+# Match http(s):// URLs and bare www. URLs
+_URL_RE = re.compile(
+    r'(https?://[^\s<>\"\'\]]+|www\.[^\s<>\"\'\]]+)',
+    re.IGNORECASE,
+)
+
+# Trailing punctuation that usually isn't part of the URL
+_TRAILING_PUNCT = re.compile(r'[.,;:!?\)]+$')
+
+
+def autolink(text):
+    """Detect URLs in plain text and wrap them in clickable <a> tags.
+
+    Escapes all content first (XSS-safe), then replaces URL patterns.
+    Returns Markup so Jinja2 won't double-escape.
+    """
+    if not text:
+        return text
+
+    escaped = str(escape(text))
+
+    def _replace(match):
+        raw = match.group(0)
+        # Strip trailing punctuation that got captured
+        trail = ''
+        m = _TRAILING_PUNCT.search(raw)
+        if m:
+            trail = m.group(0)
+            raw = raw[:m.start()]
+
+        href = raw
+        if raw.lower().startswith('www.'):
+            href = 'https://' + raw
+
+        # Truncate display text for readability
+        display = raw if len(raw) <= 60 else raw[:57] + '...'
+
+        return (
+            f'<a href="{href}" target="_blank" rel="noopener noreferrer" '
+            f'class="autolink">{display}</a>{trail}'
+        )
+
+    result = _URL_RE.sub(_replace, escaped)
+    return Markup(result)