wallet/sql: implement waddrmgr store with sqlc

[Roasbeef]

Overview

In this PR, we complete the waddrmgr side of the SQL store boundary introduced in #1293. This is the address-manager follow-up stacked on #1295, so the combined branch exercises both complete manager surfaces behind one transaction boundary.

The goal here is deliberately narrow: carry the existing durable waddrmgr state across the backend boundary without exposing walletdb buckets to SQL callers. We don't route the wallet runtime through the new store or add migration logic in this PR.

Design

The new waddrmgr interfaces cover manager metadata, sync state, key scopes, accounts, addresses, and private-key deletion. The KV adapter binds its bucket once, then delegates to the existing waddrmgr helpers and row codecs. This keeps the Bolt path on the implementation we already use today.

For SQL, both SQLite and PostgreSQL use named sqlc queries and generated query types. There is no hand-written runtime SQL or DBTX escape hatch in the manager store. The dialect-specific query trees remain separate for now, with integer widths and nullable values normalized in the backend adapters.

The store preserves the details that matter for a port-first cut:

• exact birthday block height, hash, and timestamp;
• the existing callback transaction model;
• legacy address identifiers and sticky used state;
• both default and watch-only account encodings;
• private-key deletion behavior;
• legacy waddrmgr not-found error codes.

Relationship to the Existing waddrmgr

The new waddrmgr/store.go is the persistence contract and durable state model. The new waddrmgr/store_kv.go is the thin KV adapter over db.go. Neither file replaces manager.go or adds a second address manager.

manager.go remains the behavioral layer. It owns key management, locking, scopes, accounts, address derivation, and the other wallet operations already exposed by waddrmgr. db.go remains the existing KV persistence implementation. It owns the bucket layout, legacy rows, serialization, and low-level read/write helpers.

For the KV backend, store_kv.go binds the walletdb bucket once and presents the bucket-free interface. Its methods assemble the new durable state types or translate them back into the existing rows, then call the helpers in db.go. As an example, SyncState calls the existing start-block, synced-to, birthday, and birthday-block readers. PutAddress converts an AddressState into the existing address row and calls the existing putAddress helper.

The SQL backend implements the same interface in wallet/internal/db/sqlstore, using generated sqlc queries instead of the KV adapter. The intended routing is therefore:

manager.go
    |
    v
store interface
    |
    +-- KV binding in store_kv.go -> existing db.go helpers and codecs
    |
    +-- SQL store  -> generated sqlc queries

Keeping store_kv.go in the waddrmgr package is intentional: the adapter can reuse the existing unexported helpers, row types, and codecs without exporting KV internals or creating a second implementation. Production manager.go still calls walletdb and db.go directly today. Moving those call sites behind the interface is a later integration slice. This PR only creates the complete durable boundary and proves that the old KV representation and the two SQL backends can satisfy it.

The commits retain extraction trailers for the source work so the original contribution remains visible.

Testing

• make sqlc
• pinned golangci-lint v2.4.1 against the stack base, 0 issues
• go test -count=1 ./waddrmgr ./wallet/internal/db/...
• go test -tags=test_db_postgres -count=1 ./wallet/internal/db/itest -v
• go vet ./waddrmgr ./wallet/internal/db/...

A full go test -count=1 ./... attempt passed the changed packages and stopped in chain/TestBitcoindEvents when the locally spawned bitcoind RPC endpoints refused connections.