docs: rename template file and fix vue interpolation

docs/manual/settings/voucher-templates.md

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+# Voucher Templates
+
+MIVO features a powerful template engine to create beautiful, printable vouchers.
+
+## <Icon name="FileCode" color="primary" /> Customizing Templates
+
+Templates use HTML and specialized placeholders to display voucher data.
+
+### Supported Variables
+
+| <code v-pre>{{username}}</code> | User's login username |
+| <code v-pre>{{password}}</code> | User's login password |
+| <code v-pre>{{server_name}}</code> | Hotspot server name |
+| <code v-pre>{{dns_name}}</code> | DNS name for login (e.g., `hotspot.lan`) |
+| <code v-pre>{{profile}}</code> | User profile/package name |
+| <code v-pre>{{price}}</code> | Plan price (formatted) |
+| <code v-pre>{{validity}}</code> | Validity duration |
+| <code v-pre>{{time_limit}}</code> | Time limit session |
+| <code v-pre>{{data_limit}}</code> | Data quota limit |
+| <code v-pre>{{ip_address}}</code> | User's IP address |
+| <code v-pre>{{mac_address}}</code> | User's MAC address |
+| <code v-pre>{{comment}}</code> | User comment |
+| <code v-pre>{{copyright}}</code> | Copyright text |
+| <code v-pre>{{qrcode}}</code> | Generates a QR Code for login URL |
+
+> [!TIP]
+> The <code v-pre>{{qrcode}}</code> variable supports custom attributes for styling, for example: <code v-pre>{{qrcode size=100 fg=red}}</code>.
+- **Preview**: Test your template instantly from the editor.
+
+## <Icon name="Printer" color="info" /> Quick Print
+
+Once a template is saved, it becomes available in the **Quick Print** menu within your router sessions.
+