fix(bitcoin,ui): RAM-aware dbcache to stop swap-thrash 502s + snappier status + icon placeholder

Sizes bitcoind -dbcache to host RAM (~1/16, floor 300MB, cap 4096) instead of a
fixed 2048/4096. A multi-GB UTXO cache on an 8GB node running the full app stack
pushed memory past physical RAM and triggered system-wide swap thrash: the disk
saturated, bitcoind could not answer its own RPC, and the dashboard backend's
sqlite reads stalled — surfacing as fleet-wide /rpc/v1 502s and a blank Bitcoin
UI. Applied in scripts/container-specs.sh (reconciler path) and the config.rs
bitcoin-core path.

Bitcoin status cache now polls every 5s (was 10/15) with an 8s timeout (was 20s)
and fetches the four RPCs concurrently, so the cached snapshot tracks bitcoind's
responsive windows during IBD and the UI stops dwelling on "reconnecting...".

Unifies the divergent discover AppGrid/FeaturedApps image-error handlers onto the
canonical placeholder fallback so missing app icons render the placeholder.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/src/views/discover/AppGrid.vue

@@ -157,6 +157,7 @@
 
 <script setup lang="ts">
 import type { MarketplaceApp } from './types'
+import { handleImageError } from '@/views/apps/appsConfig'
 
 defineProps<{
   filteredApps: MarketplaceApp[]
@@ -181,11 +182,6 @@ defineEmits<{
   'install': [app: MarketplaceApp]
   'retry-nostr': []
 }>()
-
-function handleImageError(event: Event) {
-  const img = event.target as HTMLImageElement
-  img.src = '/assets/img/logo-archipelago.svg'
-}
 </script>
 
 <style scoped>

neode-ui/src/views/discover/FeaturedApps.vue

@@ -98,6 +98,7 @@
 
 <script setup lang="ts">
 import type { FeaturedApp, MarketplaceApp } from './types'
+import { handleImageError } from '@/views/apps/appsConfig'
 
 defineProps<{
   featuredApps: FeaturedApp[]
@@ -114,9 +115,4 @@ defineEmits<{
   'launch': [app: MarketplaceApp]
   'install': [app: MarketplaceApp]
 }>()
-
-function handleImageError(event: Event) {
-  const img = event.target as HTMLImageElement
-  img.src = '/assets/img/logo-archipelago.svg'
-}
 </script>