feat: Google Photos provider backend + API hardening

- Add Google Photos provider: client, models, change detector, capabilities
- Add notification templates (en/ru) for all GP event slots
- Add command templates (en/ru) for GP bot commands
- Register GP in slot/command loaders, capabilities, and seeds
- Harden provider API: validate OAuth credentials on create/update
- Add internal URL rewriting for asset fetches (LAN optimization)
- Fix template renderer to handle missing variables gracefully
- Improve webhook command routing for multi-provider support
- Add provider health check endpoint and watcher improvements

frontend/src/lib/components/SearchPalette.svelte

@@ -136,6 +136,7 @@
 	});
 
 	const flatResults = $derived(results);
+	const flatIndexMap = $derived(new Map(flatResults.map((item, idx) => [item, idx])));
 
 	async function openPalette() {
 		open = true;
@@ -239,7 +240,7 @@
 						{group.label}
 					</div>
 					{#each group.items as item, i}
-						{@const flatIdx = flatResults.indexOf(item)}
+						{@const flatIdx = flatIndexMap.get(item) ?? -1}
 						<button
 							class="sp-item"
 							class:sp-active={flatIdx === activeIndex}