Wissensdatenbank: Markdown, FTS5-Suche, Sanitizing, UX

- Markdown-Rendering fuer Notizen (fett, kursiv, Ueberschriften, Listen, Code, Links)
- HTML-Sanitizing im Frontend und Backend (XSS-Schutz)
- FTS5 Volltextindex fuer schnelle Suche mit Ranking
- Kategorie-Loeschung zeigt Anzahl betroffener Eintraege

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

frontend/css/knowledge.css

@@ -441,6 +441,84 @@
   white-space: pre-wrap;
 }
 
+/* Markdown Styles in Notizen */
+.knowledge-entry-notes h1 {
+  font-size: 1.2rem;
+  font-weight: 700;
+  color: var(--text-primary);
+  margin: 0.5rem 0 0.25rem 0;
+}
+
+.knowledge-entry-notes h2 {
+  font-size: 1.1rem;
+  font-weight: 600;
+  color: var(--text-primary);
+  margin: 0.5rem 0 0.25rem 0;
+}
+
+.knowledge-entry-notes h3 {
+  font-size: 1rem;
+  font-weight: 600;
+  color: var(--text-primary);
+  margin: 0.4rem 0 0.2rem 0;
+}
+
+.knowledge-entry-notes code {
+  background: var(--bg-tertiary);
+  padding: 2px 6px;
+  border-radius: var(--radius-sm);
+  font-family: 'Courier New', monospace;
+  font-size: 0.85em;
+}
+
+.knowledge-entry-notes pre {
+  background: var(--bg-tertiary);
+  padding: var(--spacing-sm) var(--spacing-md);
+  border-radius: var(--radius-md);
+  overflow-x: auto;
+  margin: 0.5rem 0;
+}
+
+.knowledge-entry-notes pre code {
+  background: transparent;
+  padding: 0;
+  border-radius: 0;
+  font-size: 0.85rem;
+  line-height: 1.5;
+}
+
+.knowledge-entry-notes ul,
+.knowledge-entry-notes ol {
+  padding-left: 1.5rem;
+  margin: 0.25rem 0;
+}
+
+.knowledge-entry-notes li {
+  margin: 0.15rem 0;
+}
+
+.knowledge-entry-notes a {
+  color: var(--primary);
+  text-decoration: underline;
+}
+
+.knowledge-entry-notes a:hover {
+  opacity: 0.8;
+}
+
+.knowledge-entry-notes strong {
+  font-weight: 700;
+  color: var(--text-primary);
+}
+
+.knowledge-entry-notes em {
+  font-style: italic;
+}
+
+.knowledge-entry-notes p {
+  margin: 0.25rem 0;
+}
+
 .knowledge-entry-attachments-info {
   display: flex;
   align-items: center;