[Feature Request] Pin panel to fixed position in dashboard

## Feature Request ### Use Case When working with large dashboards that have many panels, users often need to scroll back up to filter/search panels every time they want to adjust criteria. This interrupts the workflow when viewing results in panels further down the dashboard. This is particularly impactful for panels that control dashboard variables (like search/filter panels), where users frequently need to adjust values while viewing results elsewhere. ### Proposed Solution Add the ability to pin a panel to a fixed position in the dashboard viewport: 1. **Pin toggle option** in panel settings (similar to how rows can be collapsed) 2. **Fixed positioning** - When pinned, the panel stays visible at the top of the viewport while scrolling 3. **Visual indicator** showing the panel is pinned 4. **Configurable position** - Allow pinning to top, bottom, or side of viewport ### Alternatives Considered - Duplicating panels at multiple positions (clutters the layout, maintenance overhead) - Browser extensions to pin elements (not portable across users/browsers) - Sticky rows (current Grafana feature, but applies to entire rows, not individual panels) ### Context This feature would significantly improve UX for dashboards with many panels where search/filter criteria need frequent adjustment. It's especially valuable for: - Operations dashboards with many metrics - Search panels that control dashboard variables - Filter panels in complex monitoring setups ### Related This request originated from a Grafana panel plugin community request: https://github.com/matheus-meneses/grafana-dynamic-search/issues/43