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/stlp.yaml

@@ -0,0 +1,74 @@
+# 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:
+      - type: grid
+        cards:
+          - type: gauge
+            entity: sensor.pfv_garage_temperature
+            name: Garage temp
+            min: 40
+            max: 110
+            unit: "°F"
+          - type: history-graph
+            title: Garage temp (24h)
+            entities:
+              - sensor.pfv_garage_temperature
+            hours_to_show: 24
+          - type: gauge
+            entity: sensor.pfv_garage_pdu_output_current
+            name: PDU output
+            unit: A
+            min: 0
+            max: 20
+          - type: entity
+            entity: sensor.pfv_garage_pdu_power
+            name: PDU power (est @120V)
+            icon: mdi:flash
+          - type: entity
+            entity: sensor.garage_pdu_daily_energy
+            name: PDU energy today
+            icon: mdi:counter
+          - type: history-graph
+            title: PDU output (24h)
+            entities:
+              - sensor.pfv_garage_pdu_output_current
+            hours_to_show: 24
+          - type: markdown
+            content: >
+              **Pending:** garage PDU outlet naming (#374), minisplit BTU
+              context (#614). Feed via tsys-librenms SNMP relay (AP7830 is
+              v1-only).