add makefile improvements and index generator

- add deploy-html, optimize-images, copy-assets targets
- add scripts/generate-index.sh for slide overview
- integrate index generation into html/build targets
- deploy to 223015c path

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/generate-index.sh

@@ -0,0 +1,88 @@
+#!/usr/bin/env bash
+# Generate index.html for slide overview
+
+BUILD_DIR="${1:-build}"
+
+cat > "$BUILD_DIR/index.html" << 'HEADER'
+<!DOCTYPE html>
+<html lang="de">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>223015c - Internettechnologien</title>
+  <style>
+    * { box-sizing: border-box; }
+    body {
+      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
+      max-width: 800px;
+      margin: 0 auto;
+      padding: 2rem;
+      background: #1a1a2e;
+      color: #eee;
+    }
+    h1 { color: #fff; margin-bottom: 0.5rem; }
+    .subtitle { color: #888; margin-bottom: 2rem; }
+    .termin {
+      background: #16213e;
+      border-radius: 8px;
+      padding: 1.5rem;
+      margin-bottom: 1rem;
+      text-decoration: none;
+      display: block;
+      transition: transform 0.2s, background 0.2s;
+    }
+    .termin:hover { background: #1f4068; transform: translateX(5px); }
+    .termin h2 { color: #fff; margin: 0 0 0.5rem 0; font-size: 1.2rem; }
+    .termin .date { color: #4ecca3; font-size: 0.9rem; }
+    .termin .topic { color: #aaa; font-size: 0.95rem; margin-left: 1rem; }
+    footer { margin-top: 2rem; color: #666; font-size: 0.85rem; text-align: center; }
+    footer a { color: #4ecca3; }
+  </style>
+</head>
+<body>
+  <h1>223015c</h1>
+  <p class="subtitle">Internettechnologien<br>
+  HdM Stuttgart - WS 2025/26 - Michael Czechowski</p>
+HEADER
+
+# Generate links for each termin (sorted)
+for html in $(ls "$BUILD_DIR"/2*.html 2>/dev/null | sort); do
+  filename=$(basename "$html")
+
+  # Extract components from filename
+  # Format: 2025-12-20-termin-1-geschichte-grundlagen-html.html
+  date=$(echo "$filename" | grep -oE '^[0-9]{4}-[0-9]{2}-[0-9]{2}')
+  termin_num=$(echo "$filename" | grep -oE 'termin-[0-9]+' | grep -oE '[0-9]+')
+  topic_raw=$(echo "$filename" | sed -E 's/^[0-9]{4}-[0-9]{2}-[0-9]{2}-termin-[0-9]+-//' | sed 's/\.html$//')
+
+  # Format topic: replace - with space, capitalize
+  topic=$(echo "$topic_raw" | sed 's/-/ /g' | sed 's/.*/\u&/')
+
+  # Format date
+  if [[ "$date" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]; then
+    formatted_date=$(date -d "$date" "+%d.%m.%Y" 2>/dev/null || echo "$date")
+  else
+    formatted_date="TBA"
+  fi
+
+  termin_label="Termin $termin_num"
+
+  cat >> "$BUILD_DIR/index.html" << LINK
+  <a href="$filename" class="termin">
+    <h2>$termin_label</h2>
+    <span class="date">$formatted_date</span>
+    <span class="topic">$topic</span>
+  </a>
+LINK
+done
+
+cat >> "$BUILD_DIR/index.html" << 'FOOTER'
+  <footer>
+    <a href="https://git.librete.ch/hdm/223015c">Git Repository</a> -
+    <a href="mailto:mail@librete.ch">Kontakt</a>
+  </footer>
+</body>
+</html>
+FOOTER
+
+echo "Generated $BUILD_DIR/index.html"