feat(dashboards): nest art room + garage under STLP dashboard [#344]

HA sidebar has no dashboard folders — nesting = one dashboard with tab
views (same pattern as Server Room). Art Room/Garage views merged into
stlp.yaml verbatim; old single-purpose dashboards removed.

https://projects.knownelement.com/issues/344

dashboards/artroom.yaml

@@ -1,32 +0,0 @@
-# Art Room dashboard [#618] — git-deployed via KNEL/pfv-bms
-# Sources: TEMPer on stlpc-artroom, Canon printer toners (IPP).
-# OctoPrint x2 + 3 3D printers land Friday (#466).
-title: Art Room
-views:
-  - title: Art Room
-    type: sections
-    sections:
-      - type: grid
-        cards:
-          - type: gauge
-            entity: sensor.pfv_artroom_temperature
-            name: Art room temp
-            min: 50
-            max: 100
-            unit: "°F"
-          - type: history-graph
-            title: Art room temp (24h)
-            entities:
-              - sensor.pfv_artroom_temperature
-            hours_to_show: 24
-          - type: entities
-            title: Printer — toner
-            entities:
-              - sensor.cnmf731c_733c_canon_cartridge_046_black_toner
-              - sensor.cnmf731c_733c_canon_cartridge_046_cyan_ton
-              - sensor.cnmf731c_733c_canon_cartridge_046_magenta_to
-              - sensor.cnmf731c_733c_canon_cartridge_046_yellow_ton
-          - type: markdown
-            content: >
-              **Pending:** TR4500 status, OctoPrint x2 + 3D printers (#466,
-              Friday).

dashboards/stlp.yaml

@@ -1,7 +1,37 @@
-# Garage dashboard [#618] — git-deployed via KNEL/pfv-bms
-# Sources: TEMPer on stlpc-garage. PDU power/temp pending integration (#374/#351).
-title: Garage
+# STLP dashboard (art room + garage) [#618/#344] — git-deployed via KNEL/pfv-bms
+# HA has no sidebar folders for dashboards; nesting = one dashboard, tab views.
+# Sources: TEMPer on stlpc-artroom / stlpc-garage, Canon printer toners (IPP),
+# garage PDU via tsys-librenms SNMP relay (AP7830 is v1-only).
+title: STLP
 views:
+  - title: Art Room
+    type: sections
+    sections:
+      - type: grid
+        cards:
+          - type: gauge
+            entity: sensor.pfv_artroom_temperature
+            name: Art room temp
+            min: 50
+            max: 100
+            unit: "°F"
+          - type: history-graph
+            title: Art room temp (24h)
+            entities:
+              - sensor.pfv_artroom_temperature
+            hours_to_show: 24
+          - type: entities
+            title: Printer — toner
+            entities:
+              - sensor.cnmf731c_733c_canon_cartridge_046_black_toner
+              - sensor.cnmf731c_733c_canon_cartridge_046_cyan_ton
+              - sensor.cnmf731c_733c_canon_cartridge_046_magenta_to
+              - sensor.cnmf731c_733c_canon_cartridge_046_yellow_ton
+          - type: markdown
+            content: >
+              **Pending:** TR4500 status, OctoPrint x2 + 3D printers (#466,
+              Friday).
+
   - title: Garage
     type: sections
     sections: