v1.0.15: fix cross-folder timer conflict + new icons

- Stop previously running timer globally using persisted runningEntryId,
  works across nested folders and plugin restarts
- In-memory cache prevents onWillAppear flash of stale running state
- Replace SVG button icons with Aurora timer PNG icons (on/off)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

com.pdma.notion-timer.sdPlugin/imgs/idle.svg

@@ -1,7 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 144 144" width="144" height="144">
-  <circle cx="72" cy="58" r="42" fill="none" stroke="#888888" stroke-width="6"/>
-  <line x1="72" y1="58" x2="72" y2="28" stroke="#888888" stroke-width="6" stroke-linecap="round"/>
-  <line x1="72" y1="58" x2="94" y2="71" stroke="#888888" stroke-width="6" stroke-linecap="round"/>
-  <line x1="62" y1="12" x2="82" y2="12" stroke="#888888" stroke-width="6" stroke-linecap="round"/>
-  <line x1="72" y1="12" x2="72" y2="20" stroke="#888888" stroke-width="6" stroke-linecap="round"/>
-</svg>

com.pdma.notion-timer.sdPlugin/imgs/running.svg

@@ -1,8 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 144 144" width="144" height="144">
-  <circle cx="72" cy="58" r="42" fill="#1a3a1a" stroke="#4caf50" stroke-width="6"/>
-  <line x1="72" y1="58" x2="72" y2="28" stroke="#4caf50" stroke-width="6" stroke-linecap="round"/>
-  <line x1="72" y1="58" x2="94" y2="71" stroke="#4caf50" stroke-width="6" stroke-linecap="round"/>
-  <line x1="62" y1="12" x2="82" y2="12" stroke="#4caf50" stroke-width="6" stroke-linecap="round"/>
-  <line x1="72" y1="12" x2="72" y2="20" stroke="#4caf50" stroke-width="6" stroke-linecap="round"/>
-  <circle cx="72" cy="58" r="5" fill="#4caf50"/>
-</svg>