Fix broken reference links and web UI bugs

- Fix RFC URLs with leading zeros (rfc0020 -> rfc20) via int filter
- Draft refs: internal link for drafts in our DB, Datatracker for external
- BCP refs: link to rfc-editor.org/info/bcpN
- Add DB connection teardown (@app.teardown_appcontext)
- Fix JS syntax error in gap_demo.html (HTML-escaped string in script tag)
- Add URL encoding to all query params in drafts.html and draft_detail.html
- Fix variable shadowing of Flask's g import in gaps_demo()
- Add None safety for ideas search data attribute

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

src/webui/templates/draft_detail.html

@@ -256,7 +256,7 @@
             </h2>
             <div class="flex flex-wrap gap-1.5">
                 {% for cat in draft.rating.categories %}
-                <a href="/drafts?cat={{ cat }}"
+                <a href="/drafts?cat={{ cat | urlencode }}"
                    class="px-2.5 py-1 rounded-full text-xs bg-slate-800/60 text-slate-400 border border-slate-700 hover:border-blue-500 hover:text-blue-400 transition">
                     {{ cat }}
                 </a>
@@ -275,16 +275,28 @@
             <div class="flex flex-wrap gap-1.5 max-h-48 overflow-y-auto">
                 {% for ref in draft.refs %}
                 {% if ref.type == 'rfc' %}
-                <a href="https://www.rfc-editor.org/rfc/{{ ref.id }}" target="_blank" rel="noopener"
+                <a href="https://www.rfc-editor.org/rfc/rfc{{ ref.id | int }}" target="_blank" rel="noopener"
                    class="px-2 py-0.5 rounded text-[10px] font-medium ref-rfc hover:opacity-80 transition">
-                    RFC {{ ref.id.replace('rfc', '') }}
+                    RFC {{ ref.id | int }}
                 </a>
                 {% elif ref.type == 'draft' %}
+                {% if ref.id in known_drafts %}
                 <a href="/drafts/{{ ref.id }}"
                    class="px-2 py-0.5 rounded text-[10px] font-medium ref-draft hover:opacity-80 transition">
                     {{ ref.id }}
                 </a>
                 {% else %}
+                <a href="https://datatracker.ietf.org/doc/{{ ref.id }}/" target="_blank" rel="noopener"
+                   class="px-2 py-0.5 rounded text-[10px] font-medium ref-draft hover:opacity-80 transition">
+                    {{ ref.id }}
+                </a>
+                {% endif %}
+                {% elif ref.type == 'bcp' %}
+                <a href="https://www.rfc-editor.org/info/bcp{{ ref.id }}" target="_blank" rel="noopener"
+                   class="px-2 py-0.5 rounded text-[10px] font-medium ref-other hover:opacity-80 transition">
+                    BCP {{ ref.id }}
+                </a>
+                {% else %}
                 <span class="px-2 py-0.5 rounded text-[10px] font-medium ref-other">
                     {{ ref.type|upper }} {{ ref.id }}
                 </span>