refactor(common): centralize extend_instance_ttl helper in mergefi_common

contracts/common/src/lib.rs

@@ -219,3 +219,19 @@ where
         .persistent()
         .extend_ttl(key, extend_to, extend_to);
 }
+
+/// Shared threshold (ledgers) before instance storage TTL extension triggers.
+pub const INSTANCE_TTL_THRESHOLD: u32 = 100_000;
+/// Shared target (ledgers) to extend instance storage TTL to.
+pub const INSTANCE_TTL_EXTEND_TO: u32 = 500_000;
+
+/// Extends the TTL of the contract's instance storage (#38). Instance
+/// storage holds Admin, Treasury, FeeBps, etc. — losing it takes down
+/// the entire contract. Uses conservative defaults suitable for a
+/// multi-month bounty lifecycle.
+pub fn extend_instance_ttl(env: &Env) {
+    env.storage()
+        .instance()
+        .extend_ttl(INSTANCE_TTL_THRESHOLD, INSTANCE_TTL_EXTEND_TO);
+}
+

contracts/escrow/src/lib.rs

@@ -774,7 +774,7 @@ pub(crate) fn extend_ttl(env: &Env, key: &DataKey) {
 /// takes down the entire contract for every issue. Uses the same
 /// threshold/extend_to as persistent records for consistency.
 pub(crate) fn extend_instance_ttl(env: &Env) {
-    env.storage().instance().extend_ttl(100_000, 500_000);
+    mergefi_common::extend_instance_ttl(env);
 }
 
 /// Extends the TTL of a persistent entry to (approximately) survive until

contracts/maintenance-pool/src/lib.rs

@@ -572,5 +572,5 @@ fn extend_ttl(env: &Env, key: &DataKey) {
 /// storage holds Admin, Treasury, and FeeBps — losing it takes down the
 /// entire contract for every pool.
 fn extend_instance_ttl(env: &Env) {
-    env.storage().instance().extend_ttl(100_000, 500_000);
+    mergefi_common::extend_instance_ttl(env);
 }

contracts/milestones/src/lib.rs

@@ -935,5 +935,5 @@ fn extend_ttl(env: &Env, key: &DataKey) {
 /// storage holds Admin, Treasury, FeeBps, and MaxSponsors — losing it
 /// takes down the entire contract for every milestone.
 fn extend_instance_ttl(env: &Env) {
-    env.storage().instance().extend_ttl(100_000, 500_000);
+    mergefi_common::extend_instance_ttl(env);
 }