Add frontend for TrackingConfig + TemplateConfig, fix locale, simplify trackers

New pages:
- /tracking-configs: Full CRUD with event tracking, asset display,
  periodic summary, scheduled assets, and memory mode sections.
  Collapsible sub-sections that show/hide based on enabled state.
- /template-configs: Full CRUD with all 21 template slots organized
  into 5 fieldsets (event messages, asset formatting, date/location,
  scheduled messages, telegram). Preview support per slot.

Updated pages:
- Targets: added tracking_config_id + template_config_id selectors
  (dropdowns populated from configs). Configs are reusable.
- Trackers: simplified to album selection + scan interval + targets.
  Added Test, Test Periodic, Test Memory buttons per tracker.
- Nav: replaced Templates with Tracking + Templates config links

Other fixes:
- Language button: now triggers window.location.reload() to force
  all child pages to re-evaluate t() calls
- Dark theme buttons: changed primary color to dark gray in dark mode
- Removed old /templates page (replaced by /template-configs)
- Added .gitignore for __pycache__ in server package

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/routes/login/+page.svelte

@@ -39,7 +39,7 @@
 	<div class="w-full max-w-sm">
 		<div class="bg-[var(--color-card)] border border-[var(--color-border)] rounded-lg p-6 shadow-sm">
 			<div class="flex justify-end gap-1 mb-4">
-				<button onclick={() => setLocale(getLocale() === 'en' ? 'ru' : 'en')}
+				<button onclick={() => { setLocale(getLocale() === 'en' ? 'ru' : 'en'); window.location.reload(); }}
 					class="text-xs px-1.5 py-0.5 rounded bg-[var(--color-muted)] text-[var(--color-muted-foreground)]">
 					{getLocale().toUpperCase()}
 				</button>