feat(sponsor): on, as blackbeard-observer.near, 30 bps to itself, 300 tx a day

blackbeard-observer.near is registered (tx At7zrH8TdYbcAmPtbjFM3RnNvSxjAZEvpJYpuvVYmir3).
Its only access key is an ML-DSA-65 key generated on bob as blackbeard;
only the public half left the host. The registrar's temporary ed25519 key
was deleted in the same transaction that added it (tx
44Ex8w8gqBUpC63pddvhR6KyV2E6PtzszZ9ngprosWoF). The operator funds the
account.

Terms, as the operator set them on blackbeard/wallet#81:
- the swap fee is 30 bps of a pool swap's input, paid to the sponsor
  account itself;
- each created account gets 0.0025 NEAR for its storage;
- at most 300 transactions a UTC day, about 1 NEAR of gas at the worst.

Refs #51

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NUx7SPonBnB3ofU4mH41WT

asset/config/config.toml.tmpl

@@ -242,14 +242,16 @@ max_gap_fill_blocks = 5000
 # `[[chains]]` entry above. "Quantus Staging Mainnet" is a different, staging
 # chain and remains deliberately unlabelled.
 
-# The NEAR sponsor for blackbeard wallets (#51, blackbeard/wallet#81). Off
-# while this stays commented out: its terms say `enabled: false` and its POSTs
-# answer 503. To turn it on:
-#   1. on bob, as blackbeard:
-#        blackbeard-cli near-sponsor-keygen /var/lib/blackbeard/near-sponsor.key
-#   2. register and fund blackbeard-observer.near, with that public key as its
-#      only access key;
-#   3. uncomment this, then restart.
+# The NEAR sponsor for blackbeard wallets (#51, blackbeard/wallet#81).
+# Commenting the section out turns it off: its terms then say
+# `enabled: false` and its POSTs answer 503. On since 2026-10-09:
+#   1. the key was made on bob, as blackbeard:
+#        blackbeard near-sponsor-keygen /var/lib/blackbeard/near-sponsor.key
+#      and only its public half ever left the host;
+#   2. blackbeard-observer.near was registered (tx At7zrH8T…) and its only key
+#      set to that one, the registrar's temporary ed25519 key deleted in the
+#      same transaction (tx 44Ex8w8g…);
+#   3. the operator funds it.
 # rpc_urls: gargravarr tracks the sponsor's shard (8) and every account it
 # creates. fee_bps is at most 50; the wallet refuses terms above that.
 # creation_deposit_yocto covers NEAR's storage for an account holding one
@@ -257,10 +259,12 @@ max_gap_fill_blocks = 5000
 # and a 42-byte b<…>.blackbeard-observer.near name adds 28, so about 210 bytes
 # at 1e19 yoctoNEAR each = 0.0021 NEAR. 0.0025 leaves room and nothing to farm.
 #
-# [near_sponsor]
-# account = "blackbeard-observer.near"
-# key_file = "/var/lib/blackbeard/near-sponsor.key"
-# rpc_urls = ["http://gargravarr.hanzalova.internal:24403", "https://rpc.mainnet.fastnear.com"]
-# fee_bps = 30
-# fee_recipient = "blackbeard-observer.near"
-# creation_deposit_yocto = "2500000000000000000000"
+[near_sponsor]
+account = "blackbeard-observer.near"
+key_file = "/var/lib/blackbeard/near-sponsor.key"
+rpc_urls = ["http://gargravarr.hanzalova.internal:24403", "https://rpc.mainnet.fastnear.com"]
+fee_bps = 30
+fee_recipient = "blackbeard-observer.near"
+creation_deposit_yocto = "2500000000000000000000"
+# 300 transactions a UTC day caps what the sponsor can burn at about 1 NEAR.
+daily_transactions = 300