server: enable ExtraBudgetForInputs to be called before full server start up

[Roasbeef]

This is a pure function that just returns what's basically a static value. There's no risk of deadlock if a caller calls into this function before the server has fully started up.

[coveralls]

Pull Request Test Coverage Report for Build 17448261145

Details

• 0 of 6 (0.0%) changed or added relevant lines in 2 files are covered.
• 52 unchanged lines in 8 files lost coverage.
• Overall coverage increased (+0.01%) to 56.883%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
server.go	0	1	0.0%
tapchannel/aux_sweeper.go	0	5	0.0%

Files with Coverage Reduction	New Missed Lines	%
tapdb/addrs.go	2	78.23%
tapdb/sqlc/transfers.sql.go	2	83.33%
itest/multisig.go	3	97.91%
tapgarden/custodian.go	5	77.02%
mssmt/compacted_tree.go	6	78.48%
tapdb/multiverse.go	6	80.59%
tapgarden/re-org_watcher.go	11	71.65%
tapdb/assets_store.go	17	79.33%

Totals
Change from base Build 17435593956:	0.01%
Covered Lines:	61510
Relevant Lines:	108135

---

💛 - Coveralls

[ffranr]

Maybe it's worth turning ExtraBudgetForInputs into a standalone function,
to make it clearer that it does not depend on s being ready. For example:

Index: tapchannel/aux_sweeper.go
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/tapchannel/aux_sweeper.go b/tapchannel/aux_sweeper.go
--- a/tapchannel/aux_sweeper.go	(revision b706a8d28c015191ffdcaae5496ab4b91692ca82)
+++ b/tapchannel/aux_sweeper.go	(date 1756895601606)
@@ -2554,9 +2554,7 @@
 
 // ExtraBudgetForInputs takes a set of inputs and maybe returns an extra budget
 // that should be added to the sweep transaction.
-func (a *AuxSweeper) ExtraBudgetForInputs(
-	inputs []input.Input) lfn.Result[btcutil.Amount] {
-
+func ExtraBudgetForInputs(inputs []input.Input) lfn.Result[btcutil.Amount] {
 	inputsWithBlobs := fn.Filter(inputs, func(i input.Input) bool {
 		return i.ResolutionBlob().IsSome()
 	})
@@ -2578,6 +2576,14 @@
 	return lfn.Ok(extraBudget)
 }
 
+// ExtraBudgetForInputs takes a set of inputs and maybe returns an extra budget
+// that should be added to the sweep transaction.
+func (a *AuxSweeper) ExtraBudgetForInputs(
+	inputs []input.Input) lfn.Result[btcutil.Amount] {
+
+	return ExtraBudgetForInputs(inputs)
+}
+
 // NotifyBroadcast is used to notify external callers of the broadcast of a
 // sweep transaction, generated by the passed BumpRequest.
 func (a *AuxSweeper) NotifyBroadcast(req *sweep.BumpRequest,
Index: server.go
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/server.go b/server.go
--- a/server.go	(revision b706a8d28c015191ffdcaae5496ab4b91692ca82)
+++ b/server.go	(date 1756895601593)
@@ -1265,11 +1265,7 @@
 	srvrLog.Tracef("ExtraBudgetForInputs called, inputs=%v",
 		lnutils.SpewLogClosure(inputs))
 
-	if err := s.waitForReady(); err != nil {
-		return lfn.Err[btcutil.Amount](err)
-	}
-
-	return s.cfg.AuxSweeper.ExtraBudgetForInputs(inputs)
+	return tapchannel.ExtraBudgetForInputs(inputs)
 }
 
 // NotifyBroadcast is used to notify external callers of the broadcast of a

[Roasbeef]

@ffranr great suggestion, will apply that

[Roasbeef]

PTAL.