Swedish adaptation: Instegscertifikat and HAREC content

- Sections and slides rewritten in Swedish; German law and institutions replaced by
  Swedish/CEPT/ITU equivalents (PTS, SSA, PTSFS 2025:1, SSMFS 2008:18), unverified
  statements marked "% TODO VERIFY"
- New toc: INSTEG, HAREC, UPPGRADERING; section idents are Swedish (see ident-map.tsv)
- Exam-question tags, BNetzA question pool, solutions and the German SWL course removed
- Static pages, snippets, applets, READMEs and image alt-texts translated
- TikZ labels translated; SVG drawings regenerated (drawing 689 still fails to build
  upstream: it references a missing photo)
- Changed from the original: not endorsed by DARC e.V., SSA or PTS

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

contents/html/applet_rectangle.html

@@ -2,11 +2,11 @@
   <script src="https://www.50ohm.de/assets/jquery/3.7.1/jquery.min.js"></script>
   <script src="https://www.50ohm.de/assets/chartjs/4.4.1/chart.min.js"></script>
 
-  <p>Hier kann die Fourier-Näherung eines symmetrischen Rechtecksignals mit einer variablen Anzahl ungerader Harmonischer untersucht werden. Die Schalter erlauben Werte von 1 bis 500.</p>
+  <p>Här kan du undersöka Fourierapproximationen av en symmetrisk fyrkantsignal med ett valbart antal udda övertoner. Reglagen tillåter värden från 1 till 500.</p>
 
   <table>
     <tr>
-      <td>Harmonische $N$:</td>
+      <td>Övertoner $N$:</td>
       <td>
         <input type="range" id="harmonicsRange" min="1" max="499" value="1" step="2">
       </td>
@@ -30,7 +30,7 @@
       data: {
         datasets: [
           {
-            label: 'Rechteck ideal',
+            label: 'Fyrkant, ideal',
             borderColor: '#ED7D71',
             backgroundColor: 'transparent',
             pointRadius: 0,
@@ -38,7 +38,7 @@
             data: []
           },
           {
-            label: 'Fourier-Näherung',
+            label: 'Fourierapproximation',
             borderColor: '#00AEDF',
             backgroundColor: 'transparent',
             pointRadius: 0,
@@ -71,7 +71,7 @@
                 if (Math.abs(value + Math.PI) < 1e-8) return '-π';
                 if (Math.abs(value - 1.5 * Math.PI) < 1e-8) return '3π/2';
                 if (Math.abs(value + 1.5 * Math.PI) < 1e-8) return '-3π/2';
-                return value.toFixed(2);
+                return value.toFixed(2).replace(".", ",");
               }
             }
           },
@@ -85,7 +85,7 @@
             ticks: {
               stepSize: 0.5,
               callback: function(value) {
-                return value.toFixed(1);
+                return value.toFixed(1).replace(".", ",");
               }
             }
           }