Initialer Commit: Kundenverwaltung (PHP/Smarty)

Bestehende Codebasis als Ausgangsstand aufgenommen.

- .gitignore: Kundendaten (uploads_*), Smarty-Compile-Cache
  (templates_c), Laufzeit-Temp und Datenbank-Dumps ausgeschlossen;
  Verzeichnisstruktur ueber .gitkeep erhalten
- .gitattributes: Zeilenenden normalisiert (LF im Repo),
  Binaerformate markiert
- db-backup.php: MySQL-Zugangsdaten kommen jetzt wie im Rest der
  Anwendung aus der externen Konfiguration statt hartkodiert aus der
  Datei; Passwort wird ueber eine temporaere Optionsdatei statt per
  Kommandozeile uebergeben, Fehler von mysqldump/gzip werden gemeldet,
  Aufraeumen aelterer Backups berechnet Jahr und Monat konsistent

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

js/tiny_mce/plugins/style/langs/en_dlg.js

@@ -0,0 +1 @@
+tinyMCE.addI18n('en.style_dlg',{"text_lineheight":"Line Height","text_variant":"Variant","text_style":"Style","text_weight":"Weight","text_size":"Size","text_font":"Font","text_props":"Text","positioning_tab":"Positioning","list_tab":"List","border_tab":"Border","box_tab":"Box","block_tab":"Block","background_tab":"Background","text_tab":"Text",apply:"Apply",title:"Edit CSS Style",clip:"Clip",placement:"Placement",overflow:"Overflow",zindex:"Z-index",visibility:"Visibility","positioning_type":"Type",position:"Position","bullet_image":"Bullet Image","list_type":"Type",color:"Color",height:"Height",width:"Width",style:"Style",margin:"Margin",left:"Left",bottom:"Bottom",right:"Right",top:"Top",same:"Same for All",padding:"Padding","box_clear":"Clear","box_float":"Float","box_height":"Height","box_width":"Width","block_display":"Display","block_whitespace":"Whitespace","block_text_indent":"Text Indent","block_text_align":"Text Align","block_vertical_alignment":"Vertical Alignment","block_letterspacing":"Letter Spacing","block_wordspacing":"Word Spacing","background_vpos":"Vertical Position","background_hpos":"Horizontal Position","background_attachment":"Attachment","background_repeat":"Repeat","background_image":"Background Image","background_color":"Background Color","text_none":"None","text_blink":"Blink","text_case":"Case","text_striketrough":"Strikethrough","text_underline":"Underline","text_overline":"Overline","text_decoration":"Decoration","text_color":"Color",text:"Text",background:"Background",block:"Block",box:"Box",border:"Border",list:"List"});