restructure: rename termin to kapitel, flatten folder structure

- rename slide files: YYYY-MM-DD-termin-N-topic.md → NN-topic.md
- flatten folders: courses/X/slides/ → slides/X/
- replace "Termin" with "Kapitel" in all content
- add klausur extraction script (make klausur)
- update Makefile, generate-index.sh, dev-server.sh
- add README.md with full documentation

scripts/generate-index.sh

@@ -77,13 +77,13 @@ cat > "$BUILD_DIR/index.html" << HEADER
       font-size: 0.875rem;
       margin-top: 0.25rem;
     }
-    .termine {
+    .kapitel {
       margin-top: 1.5rem;
       display: flex;
       flex-direction: column;
       gap: 0.75rem;
     }
-    .termin-card {
+    .kapitel-card {
       position: relative;
       background: #fff;
       border-radius: 12px;
@@ -94,31 +94,31 @@ cat > "$BUILD_DIR/index.html" << HEADER
       align-items: center;
       gap: 1rem;
     }
-    .termin-card:hover {
+    .kapitel-card:hover {
       transform: translateY(-2px);
       box-shadow: 0 4px 12px rgba(0,0,0,0.12);
     }
-    .termin-link {
+    .kapitel-link {
       display: block;
       padding: 1.25rem 1.5rem;
       text-decoration: none;
       color: inherit;
       grid-column: 1;
     }
-    .termin-label {
+    .kapitel-label {
       font-size: 0.7rem;
       font-weight: 600;
       color: $ACCENT_COLOR;
       text-transform: uppercase;
       letter-spacing: 0.05em;
     }
-    .termin-title {
+    .kapitel-title {
       font-size: 1.05rem;
       font-weight: 500;
       color: #1d1d1f;
       margin: 0.15rem 0;
     }
-    .termin-date {
+    .kapitel-date {
       font-size: 0.8rem;
       color: #86868b;
     }
@@ -151,7 +151,7 @@ cat > "$BUILD_DIR/index.html" << HEADER
     }
     .btn-pdf:hover { background: #e8e8ed; }
     /* Make entire card clickable via overlay */
-    .termin-link::after {
+    .kapitel-link::after {
       content: '';
       position: absolute;
       inset: 0;
@@ -184,10 +184,10 @@ cat > "$BUILD_DIR/index.html" << HEADER
       color: #86868b;
     }
     @media (max-width: 600px) {
-      .termin-card {
+      .kapitel-card {
         grid-template-columns: 1fr;
       }
-      .termin-link {
+      .kapitel-link {
         padding-bottom: 0.75rem;
       }
       .btn-slides, .btn-pdf {
@@ -205,14 +205,13 @@ cat > "$BUILD_DIR/index.html" << HEADER
   <div class="termine">
 HEADER
 
-# Generate links for each termin (sorted)
-for html in $(ls "$BUILD_DIR"/2*.html 2>/dev/null | sort); do
+# Generate links for each kapitel (sorted)
+for html in $(ls "$BUILD_DIR"/[0-9][0-9]-*.html 2>/dev/null | sort); do
   filename=$(basename "$html")
 
-  # Extract components from filename
-  date=$(echo "$filename" | grep -oE '^[0-9]{4}-[0-9x]{2}-[0-9x]{2}')
-  termin_num=$(echo "$filename" | grep -oE 'termin-[0-9]+' | grep -oE '[0-9]+')
-  topic_raw=$(echo "$filename" | sed -E 's/^[0-9]{4}-[0-9x]{2}-[0-9x]{2}-termin-[0-9]+-//' | sed 's/\.html$//')
+  # Extract components from filename (format: NN-topic.html)
+  kapitel_num=$(echo "$filename" | grep -oE '^[0-9]+' | sed 's/^0*//')
+  topic_raw=$(echo "$filename" | sed -E 's/^[0-9]+-//' | sed 's/\.html$//')
 
   # Look up nice topic name or fallback
   topic="${TOPIC_MAP[$topic_raw]}"
@@ -220,18 +219,11 @@ for html in $(ls "$BUILD_DIR"/2*.html 2>/dev/null | sort); do
     topic=$(echo "$topic_raw" | sed 's/-/ /g' | sed 's/.*/\u&/')
   fi
 
-  # Format date
-  if [[ "$date" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]] && [[ ! "$date" =~ xx ]]; then
-    formatted_date=$(date -d "$date" "+%d. %B %Y" 2>/dev/null || echo "$date")
+  # Handle kapitel number
+  if [[ "$kapitel_num" == "0" ]] || [[ -z "$kapitel_num" ]]; then
+    kapitel_label="Einführung"
   else
-    formatted_date="Termin folgt"
-  fi
-
-  # Handle termin number
-  if [[ "$termin_num" == "0" ]]; then
-    termin_label="Einführung"
-  else
-    termin_label="Termin $termin_num"
+    kapitel_label="Kapitel $kapitel_num"
   fi
 
   pdf_filename="${filename%.html}.pdf"
@@ -243,11 +235,10 @@ for html in $(ls "$BUILD_DIR"/2*.html 2>/dev/null | sort); do
   fi
 
   cat >> "$BUILD_DIR/index.html" << LINK
-    <div class="termin-card">
-      <a href="$filename" class="termin-link">
-        <div class="termin-label">$termin_label</div>
-        <div class="termin-title">$topic</div>
-        <div class="termin-date">$formatted_date</div>
+    <div class="kapitel-card">
+      <a href="$filename" class="kapitel-link">
+        <div class="kapitel-label">$kapitel_label</div>
+        <div class="kapitel-title">$topic</div>
       </a>
       <a href="$filename" class="btn btn-slides">Folien</a>
       $pdf_link