fix: increase Bitcoin memory limit to 4g, reduce dbcache to 2048

Bitcoin Knots needs more memory headroom (was OOMing at 2g during IBD).
Reduce dbcache from 4096 to 2048 on large disks to stay within the 4g
container limit. Low-memory systems get 2g (was 1g).

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

core/archipelago/src/api/rpc/package/config.rs

@@ -255,7 +255,7 @@ pub(super) fn get_health_check_args(app_id: &str, rpc_pass: &str) -> Vec<String>
 pub(super) fn get_memory_limit(app_id: &str) -> &'static str {
     match app_id {
         // Heavy apps
-        "bitcoin" | "bitcoin-core" | "bitcoin-knots" => "2g",
+        "bitcoin" | "bitcoin-core" | "bitcoin-knots" => "4g",
         "onlyoffice" | "onlyoffice-documentserver" => "2g",
         "ollama" => "4g",
         // Medium apps