Fix broken source links caused by LLM-generated letter suffixes (e.g. 1383a)

The LLM occasionally generates source references with letter suffixes
(e.g. [1383a], [1396b]) despite being instructed not to. This caused
broken links because the sources array only contained integer nr values.

Backend: Add _sanitize_sources() to strip letter suffixes after parsing
and deduplicate, preferring entries with valid URLs.

Frontend: Add fallback in citation renderer - when a suffix reference
like [1383a] has no matching source with URL, fall back to the base
number [1383].

Also cleaned up 99 broken suffix entries and 44 suffix references in
the Irankonflikt incident (ID 6) database records.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/static/js/components.js

@@ -444,10 +444,17 @@ const UI = {
         html = html.replace(/<\/ul>(<br>)+/g, '</ul>');
         html = html.replace(/(<br>){2,}/g, '<br>');
 
-        // Inline-Zitate [1], [2] etc. als klickbare Links rendern
+        // Inline-Zitate [1], [2], [1383a] etc. als klickbare Links rendern
         if (sources.length > 0) {
             html = html.replace(/\[(\d+[a-z]?)\]/g, (match, num) => {
-                const src = sources.find(s => String(s.nr) === num || Number(s.nr) === Number(num));
+                // Exakte Suche (auch mit Buchstaben-Suffix)
+                let src = sources.find(s => String(s.nr) === num || Number(s.nr) === Number(num));
+                // Fallback: Bei Suffix wie "1383a" auf Basisnummer 1383 zurueckfallen
+                if ((!src || !src.url) && /[a-z]$/.test(num)) {
+                    const baseNum = num.replace(/[a-z]$/, '');
+                    const baseSrc = sources.find(s => String(s.nr) === baseNum || Number(s.nr) === Number(baseNum));
+                    if (baseSrc && baseSrc.url) src = baseSrc;
+                }
                 if (src && src.url) {
                     return `<a href="${this.escape(src.url)}" target="_blank" rel="noopener" class="citation" title="${this.escape(src.name)}">[${num}]</a>`;
                 }