feat: Timestamps + LaTeX/KaTeX-Rendering im Chat

Timestamps (dd.MM.yyyy HH:mm:ss):
- Neuer _formatTimestamp() + _addTimestamp() Helper in ui.js
- Timestamp bei allen User- und Assistant-Nachrichten (live, history, archiv)
- Erscheint on hover, halbtransparent, rechts oben an der Bubble

LaTeX/Math-Rendering mit KaTeX 0.16.21:
- KaTeX lokal eingebunden (JS + CSS + 21 woff2-Fonts)
- renderMarkdown() schützt LaTeX vor Markdown-Parsing
- $$...$$ → Block-Math (zentriert), $...$ → Inline-Math
- Fehlerhafte Ausdrücke als <code> Fallback
- KaTeX-Display Styling in markdown.css

Weitere Änderungen:
- theme.css: Neue --info Farbe
- Blockquote-Styling: info-Farbe statt halbtransparent

wwwroot/css/chat.css

@@ -412,6 +412,7 @@
   position: relative;
 }
 
+.msg-timestamp,
 .msg-reply-btn,
 .msg-delete-btn,
 .msg-mark-btn,
@@ -420,12 +421,17 @@
   top: var(--badge-spacing);
   opacity: 0;
   transition: opacity var(--transition-duration);
-  padding: .1em .3em;
   font-size: var(--font-size);
-  background: var(--f2-bg);
-  border: var(--border-width) solid var(--f2-border);
-  border-radius: var(--border-radius);
   z-index: 1;
+  white-space: nowrap;
+}
+
+.msg-timestamp {
+  padding: .25em .6em;
+  border-radius: var(--border-radius);
+  right: calc(var(--badge-spacing) + 8em + var(--badge-spacing) * 2);
+  pointer-events: none;
+  background: var(--f3-bg);
 }
 
 .msg-reply-btn {
@@ -444,6 +450,7 @@
   right: var(--badge-spacing);
 }
 
+.msg:hover .msg-timestamp,
 .msg:hover .msg-reply-btn,
 .msg:hover .msg-delete-btn,
 .msg:hover .msg-mark-btn,

wwwroot/css/fonts/KaTeX_Math-Regular.woff2

@@ -0,0 +1 @@
+Couldn't find the requested file /dist/fonts/KaTeX_Math-Regular.woff2 in katex.

wwwroot/css/katex.min.css

@@ -0,0 +1 @@
+@font-face{font-family:KaTeX_AMS;font-style:normal;font-weight:400;src:url(fonts/KaTeX_AMS-Regular.woff2) format("woff2"),url(fonts/KaTeX_AMS-Regular.woff) format("woff"),url(fonts/KaTeX_AMS-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Caligraphic;font-style:normal;font-weight:700;src:url(fonts/KaTeX_Caligraphic-Bold.woff2) format("woff2"),url(fonts/KaTeX_Caligraphic-Bold.woff) format("woff"),url(fonts/KaTeX_Caligraphic-Bold.ttf) format("truetype")}@font-face{font-family:KaTeX_Caligraphic;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Caligraphic-Regular.woff2) format("woff2"),url(fonts/KaTeX_Caligraphic-Regular.woff) format("woff"),url(fonts/KaTeX_Caligraphic-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Fraktur;font-style:normal;font-weight:700;src:url(fonts/KaTeX_Fraktur-Bold.woff2) format("woff2"),url(fonts/KaTeX_Fraktur-Bold.woff) format("woff"),url(fonts/KaTeX_Fraktur-Bold.ttf) format("truetype")}@font-face{font-family:KaTeX_Fraktur;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Fraktur-Regular.woff2) format("woff2"),url(fonts/KaTeX_Fraktur-Regular.woff) format("woff"),url(fonts/KaTeX_Fraktur-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Main;font-style:normal;font-weight:700;src:url(fonts/KaTeX_Main-Bold.woff2) format("woff2"),url(fonts/KaTeX_Main-Bold.woff) format("woff"),url(fonts/KaTeX_Main-Bold.ttf) format("truetype")}@font-face{font-family:KaTeX_Main;font-style:italic;font-weight:700;src:url(fonts/KaTeX_Main-BoldItalic.woff2) format("woff2"),url(fonts/KaTeX_Main-BoldItalic.woff) format("woff"),url(fonts/KaTeX_Main-BoldItalic.ttf) format("truetype")}@font-face{font-family:KaTeX_Main;font-style:italic;font-weight:400;src:url(fonts/KaTeX_Main-Italic.woff2) format("woff2"),url(fonts/KaTeX_Main-Italic.woff) format("woff"),url(fonts/KaTeX_Main-Italic.ttf) format("truetype")}@font-face{font-family:KaTeX_Main;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Main-Regular.woff2) format("woff2"),url(fonts/KaTeX_Main-Regular.woff) format("woff"),url(fonts/KaTeX_Main-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Math;font-style:italic;font-weight:700;src:url(fonts/KaTeX_Math-BoldItalic.woff2) format("woff2"),url(fonts/KaTeX_Math-BoldItalic.woff) format("woff"),url(fonts/KaTeX_Math-BoldItalic.ttf) format("truetype")}@font-face{font-family:KaTeX_Math;font-style:italic;font-weight:400;src:url(fonts/KaTeX_Math-Italic.woff2) format("woff2"),url(fonts/KaTeX_Math-Italic.woff) format("woff"),url(fonts/KaTeX_Math-Italic.ttf) format("truetype")}@font-face{font-family:"KaTeX_SansSerif";font-style:normal;font-weight:700;src:url(fonts/KaTeX_SansSerif-Bold.woff2) format("woff2"),url(fonts/KaTeX_SansSerif-Bold.woff) format("woff"),url(fonts/KaTeX_SansSerif-Bold.ttf) format("truetype")}@font-face{font-family:"KaTeX_SansSerif";font-style:italic;font-weight:400;src:url(fonts/KaTeX_SansSerif-Italic.woff2) format("woff2"),url(fonts/KaTeX_SansSerif-Italic.woff) format("woff"),url(fonts/KaTeX_SansSerif-Italic.ttf) format("truetype")}@font-face{font-family:"KaTeX_SansSerif";font-style:normal;font-weight:400;src:url(fonts/KaTeX_SansSerif-Regular.woff2) format("woff2"),url(fonts/KaTeX_SansSerif-Regular.woff) format("woff"),url(fonts/KaTeX_SansSerif-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Script;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Script-Regular.woff2) format("woff2"),url(fonts/KaTeX_Script-Regular.woff) format("woff"),url(fonts/KaTeX_Script-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Size1;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Size1-Regular.woff2) format("woff2"),url(fonts/KaTeX_Size1-Regular.woff) format("woff"),url(fonts/KaTeX_Size1-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Size2;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Size2-Regular.woff2) format("woff2"),url(fonts/KaTeX_Size2-Regular.woff) format("woff"),url(fonts/KaTeX_Size2-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Size3;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Size3-Regular.woff2) format("woff2"),url(fonts/KaTeX_Size3-Regular.woff) format("woff"),url(fonts/KaTeX_Size3-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Size4;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Size4-Regular.woff2) format("woff2"),url(fonts/KaTeX_Size4-Regular.woff) format("woff"),url(fonts/KaTeX_Size4-Regular.ttf) format("truetype")}@font-face{font-family:KaTeX_Typewriter;font-style:normal;font-weight:400;src:url(fonts/KaTeX_Typewriter-Regular.woff2) format("woff2"),url(fonts/KaTeX_Typewriter-Regular.woff) format("woff"),url(fonts/KaTeX_Typewriter-Regular.ttf) format("truetype")}.katex{font:normal 1.21em KaTeX_Main,Times New Roman,serif;line-height:1.2;text-indent:0;text-rendering:auto}.katex *{-ms-high-contrast-adjust:none!important;border-color:currentColor}.katex .katex-version:after{content:"0.16.21"}.katex .katex-mathml{clip:rect(1px,1px,1px,1px);border:0;height:1pLine truncated

wwwroot/css/markdown.css

@@ -84,10 +84,10 @@
 }
 
 .markdown blockquote {
-  border-left: 3px solid var(--f3-border);
+  border-left: 3px solid var(--info);
   margin: 0 0 .5em 0;
   padding: .5em;
-  opacity: var(--semi-transparent);
+  color: var(--info);
 }
 
 .markdown blockquote:last-child {
@@ -134,6 +134,33 @@
   margin-right: .5em;
 }
 
+/* KaTeX Math */
+
+.markdown .katex-display {
+  margin: .75em .25em;
+  overflow-x: auto;
+  overflow-y: hidden;
+  padding: .25em 0;
+  text-align: left;
+  font-size: 1.1em;
+}
+
+.markdown .katex-display:first-child {
+  margin-top: 0;
+}
+
+.markdown .katex-display:last-child {
+  margin-bottom: 0;
+}
+
+.markdown .katex {
+  text-align: left;
+}
+
+.markdown .katex-error {
+  color: var(--dangerous);
+}
+
 /* Fluent Emoji */
 
 img.fluent-emoji {

wwwroot/css/theme.css

@@ -5,6 +5,7 @@
   --secondary: #4a1;
   --dangerous: #c53;
   --warning: #fa0;
+  --info: #99c;
   --f1-bg: #111;
   --f1-border: #333;
   --f2-bg: #222;