tips: grin config gate, reorg sweep_txid preservation, LWS import retry

- config: grin is a supported tip chain (voucher model verified against the node),
  so FEATURE_TIPS with only grin enabled no longer fails closed at boot.
- social_tips: revert_sweep_on_reorg now preserves sweep_txid instead of nulling
  it. Address-scan chains (btc/ltc/xmr/wow) overwrite it via confirm_sweep_onchain
  on the next cycle, so preserving the orphaned value is harmless; grin needs the
  kernel excess to re-date a re-mined sweep via get_kernel, so nulling it stranded
  reorged grin tips in 'claiming'. Test updated to assert preservation.
- lws import_account: retry the birthday backfill rescan (3 attempts, backoff) so
  a transient failure no longer strands a new account at the chain tip. The
  already-registered Some(_) no-op is unchanged, so this cannot reintroduce the
  balance-reset bug.

src/config.rs

@@ -1105,14 +1105,14 @@ impl Config {
         // Public tips escrow on-chain and deliver by share URL, so an instance
         // with FEATURE_TIPS on but no chain to escrow on, or no TIP_SHARE_BASE_URL
         // to build share links from, would advertise a tips subsystem it cannot
-        // actually serve. Fail closed rather than boot broken. (Grin is out of the
-        // tips port, so it is NOT a supported tip chain here.)
+        // actually serve. Fail closed rather than boot broken. Grin tips (voucher
+        // model, verified against the grin node) are supported, so grin counts.
         if self.features.tips {
             let c = &self.features.chains;
-            if !(c.btc || c.ltc || c.xmr || c.wow) {
+            if !(c.btc || c.ltc || c.xmr || c.wow || c.grin) {
                 return Err(cfg_err(
-                    "FEATURE_TIPS is on but no supported tip chain is enabled — enable at least \
-                     one of FEATURE_BTC / FEATURE_LTC / FEATURE_XMR / FEATURE_WOW",
+                    "FEATURE_TIPS is on but no supported tip chain is enabled: enable at least \
+                     one of FEATURE_BTC / FEATURE_LTC / FEATURE_XMR / FEATURE_WOW / FEATURE_GRIN",
                 ));
             }
             if self.tip_share_base.is_none() {

src/infra/db/social_tips.rs

@@ -694,12 +694,20 @@ impl Database {
     }
 
     /// Revert a settled (`claimed`) tip back to `claiming` after a reorg orphaned
-    /// its recorded sweep. Clearing `sweep_txid` is LOAD-BEARING: the next
-    /// confirm cycle re-scans the address and records the NEW on-chain winner,
-    /// not the orphaned one. Also clears `sweep_confirmed_dm_sent_at` so a fresh
-    /// "claimed" notify can fire once re-confirmation lands. The
-    /// `status = 'claimed' AND sweep_confirmed_at IS NOT NULL` guard is the only
-    /// path off `claimed`; `None` if the row isn't settled.
+    /// its recorded sweep. Clears the settlement markers (`sweep_confirmed_at`,
+    /// block height/hash) and `sweep_confirmed_dm_sent_at` so a fresh "claimed"
+    /// notify can fire once re-confirmation lands.
+    ///
+    /// `sweep_txid` is deliberately PRESERVED. For address-scan chains
+    /// (btc/ltc/xmr/wow) the next confirm cycle re-scans the address and
+    /// `confirm_sweep_onchain` overwrites `sweep_txid` with the new on-chain
+    /// winner, so preserving the orphaned value is harmless. For grin (voucher)
+    /// it is REQUIRED: `probe_grin_spends` dates the re-mined sweep via
+    /// `get_kernel(sweep_txid /* = kernel excess */)`, so nulling it would strand
+    /// the row in `claiming` forever after a reorg.
+    ///
+    /// The `status = 'claimed' AND sweep_confirmed_at IS NOT NULL` guard is the
+    /// only path off `claimed`; `None` if the row isn't settled.
     #[instrument(skip(self))]
     pub async fn revert_sweep_on_reorg(
         &self,
@@ -709,7 +717,6 @@ impl Database {
             "UPDATE social_tips \
              SET status = 'claiming', \
                  sweep_confirmed_at = NULL, \
-                 sweep_txid = NULL, \
                  sweep_block_height = NULL, \
                  sweep_block_hash = NULL, \
                  sweep_confirmed_dm_sent_at = NULL, \

src/infra/lws/client.rs

@@ -245,7 +245,28 @@ impl LwsClient {
                 let current =
                     self.account_scan_height(address).await?.unwrap_or(u64::MAX);
                 if start_height < current {
-                    self.rescan(vec![address.to_string()], start_height).await?;
+                    // The account is now added at the chain tip. If this backfill
+                    // rescan fails, the account is stranded at the tip: it reads a
+                    // 0 balance and the `Some(_)` short-circuit above (which exists
+                    // to prevent the reset loop) means a later re-registration will
+                    // NOT retry it. So retry a transient failure here, where we
+                    // still know this is a fresh account that owes a backwards scan.
+                    let mut attempt = 0u32;
+                    loop {
+                        match self.rescan(vec![address.to_string()], start_height).await {
+                            Ok(()) => break,
+                            Err(e) => {
+                                attempt += 1;
+                                if attempt >= 3 {
+                                    return Err(e);
+                                }
+                                tokio::time::sleep(std::time::Duration::from_millis(
+                                    300 * u64::from(attempt),
+                                ))
+                                .await;
+                            }
+                        }
+                    }
                 }
                 Ok(())
             }