223015b: container-vs-codec eigene demo + CJK-fonts + daten-grundlagen rename + reword punkt-platzhalter

user-feedback issues:
1. container-codec-diagram.png war stock-asset (vermutlich aus lehrbuch übernommen) — user: 'das kannst du nicht wiederverwenden, bau deine eigene grafik'
   → neue demo container-vs-codec.html mit zwei .mp4-containern side-by-side, je 4 spuren (video lila, audio orange, untertitel grün, meta grau): datei A älterer stand (H.264/AAC/TTML), datei B modern (AV1/Opus/WebVTT+HDR). verdict 'gleiche endung, anderes innenleben + mediainfo zeigt beides'. dashed-border-container + farbige spur-rahmen. eigener stil

2. CJK-zeichen (中, こんにちは) pixelig (unifont bitmap) statt sauberer fonts
   → google-fonts @import (Noto Sans JP + SC) + font-family in body + code-tags

3. 'Datenfundamentale' kein deutsches wort (nicht im duden)
   → git mv 01-datenfundamentale.md → 01-daten-grundlagen.md (+bogen-doc), Makefile aktualisiert, text-replace in 4 docs

4. 'Hex-Editoren zeigen \`.\` als Platzhalter' kleiner punkt schwer lesbar
   → 'zeigen einen Punkt oder ein anderes Ersatzzeichen'

klausurfolien regeneriert (27 slides)

slides/223015b/assets/demos/container-vs-codec.html

@@ -0,0 +1,172 @@
+<!DOCTYPE html>
+<html lang="de">
+<head>
+<meta charset="UTF-8">
+<title>Container ≠ Codec</title>
+<style>
+  :root {
+    --dark: #1a1a2e;
+    --muted: #6b7280;
+    --soft: #f8fafc;
+    --border: #cbd5e1;
+    --hl: #d63384;
+    --container: #2563eb;
+    --video: #7c3aed;
+    --audio: #ea580c;
+    --subs: #16a34a;
+    --meta: #94a3b8;
+  }
+  html, body { margin: 0; padding: 0; background: #fff; font-family: system-ui, -apple-system, sans-serif; color: var(--dark); }
+  body { padding: 28px 40px; }
+  h1 { text-align: center; margin: 0 0 6px; font-size: 1.75rem; }
+  .sub { text-align: center; color: var(--muted); margin-bottom: 22px; font-size: 1.05rem; }
+  .sub strong { color: var(--dark); }
+
+  .scene {
+    display: grid;
+    grid-template-columns: 1fr 1fr;
+    gap: 22px;
+    max-width: 1200px;
+    margin: 0 auto;
+  }
+
+  .container-box {
+    border: 3px dashed var(--container);
+    border-radius: 14px;
+    padding: 14px 16px 18px;
+    background: #fff;
+    position: relative;
+  }
+  .container-tag {
+    position: absolute;
+    top: -12px;
+    left: 18px;
+    background: #fff;
+    padding: 0 10px;
+    font-family: ui-monospace, monospace;
+    font-size: 0.78rem;
+    font-weight: 700;
+    color: var(--container);
+  }
+  .container-label {
+    text-align: center;
+    font-size: 0.7rem;
+    font-weight: 700;
+    text-transform: uppercase;
+    letter-spacing: 0.12em;
+    color: var(--muted);
+    margin-bottom: 10px;
+  }
+
+  .track {
+    display: grid;
+    grid-template-columns: 90px 1fr;
+    gap: 12px;
+    align-items: center;
+    background: var(--soft);
+    border-left: 4px solid;
+    border-radius: 6px;
+    padding: 9px 14px;
+    margin-bottom: 6px;
+  }
+  .track.video { border-left-color: var(--video); }
+  .track.audio { border-left-color: var(--audio); }
+  .track.subs  { border-left-color: var(--subs); }
+  .track.meta  { border-left-color: var(--meta); }
+
+  .track-label {
+    font-size: 0.78rem;
+    font-weight: 700;
+    text-transform: uppercase;
+    letter-spacing: 0.08em;
+  }
+  .track.video .track-label { color: var(--video); }
+  .track.audio .track-label { color: var(--audio); }
+  .track.subs  .track-label { color: var(--subs); }
+  .track.meta  .track-label { color: var(--meta); }
+
+  .codec-pill {
+    display: inline-block;
+    font-family: ui-monospace, monospace;
+    font-size: 0.82rem;
+    background: #fff;
+    border: 1px solid var(--border);
+    padding: 2px 9px;
+    border-radius: 4px;
+    color: var(--dark);
+  }
+
+  .verdict {
+    margin-top: 22px;
+    max-width: 1200px;
+    margin-left: auto;
+    margin-right: auto;
+    text-align: center;
+    border: 2px solid var(--hl);
+    border-radius: 12px;
+    padding: 14px 22px;
+  }
+  .verdict-q { font-size: 1.1rem; font-weight: 700; color: var(--hl); }
+  .verdict-a { font-size: 0.93rem; color: var(--dark); margin-top: 4px; }
+  .verdict-a strong { color: var(--hl); }
+  .verdict-a code { font-family: ui-monospace, monospace; background: var(--soft); padding: 1px 5px; border-radius: 4px; }
+</style>
+</head>
+<body>
+  <h1>Container ≠ Codec</h1>
+  <div class="sub">Die <strong>Hülle</strong> sagt nichts darüber, <strong>wie</strong> der Inhalt komprimiert wurde.</div>
+
+  <div class="scene">
+
+    <div class="container-box">
+      <span class="container-tag">.mp4</span>
+      <div class="container-label">Datei A — älterer Stand</div>
+
+      <div class="track video">
+        <span class="track-label">Video</span>
+        <span><span class="codec-pill">H.264 / AVC</span> · 1080p · 8 Mbit/s</span>
+      </div>
+      <div class="track audio">
+        <span class="track-label">Audio</span>
+        <span><span class="codec-pill">AAC</span> · 192 kbit/s · Stereo</span>
+      </div>
+      <div class="track subs">
+        <span class="track-label">Untertitel</span>
+        <span><span class="codec-pill">TTML</span> · de + en</span>
+      </div>
+      <div class="track meta">
+        <span class="track-label">Metadaten</span>
+        <span>Titel · Dauer · Datum · Bitrate</span>
+      </div>
+    </div>
+
+    <div class="container-box">
+      <span class="container-tag">.mp4</span>
+      <div class="container-label">Datei B — modern</div>
+
+      <div class="track video">
+        <span class="track-label">Video</span>
+        <span><span class="codec-pill">AV1</span> · 4K · 25 Mbit/s</span>
+      </div>
+      <div class="track audio">
+        <span class="track-label">Audio</span>
+        <span><span class="codec-pill">Opus</span> · 128 kbit/s · 5.1 Surround</span>
+      </div>
+      <div class="track subs">
+        <span class="track-label">Untertitel</span>
+        <span><span class="codec-pill">WebVTT</span> · de + en + ja</span>
+      </div>
+      <div class="track meta">
+        <span class="track-label">Metadaten</span>
+        <span>Titel · Dauer · Datum · HDR-Info</span>
+      </div>
+    </div>
+
+  </div>
+
+  <div class="verdict">
+    <div class="verdict-q">Gleiche Endung. Anderes Innenleben.</div>
+    <div class="verdict-a"><strong>Container</strong> = Verpackung (<code>.mp4</code>, <code>.mkv</code>, <code>.webm</code>). <strong>Codec</strong> = Komprimierer (H.264 / AV1 / AAC / Opus). <strong>Tool:</strong> <code>mediainfo &lt;datei&gt;</code> zeigt beides.</div>
+  </div>
+</body>
+</html>