Migrate db and config to mcdsl

- db.Open: delegate to mcdsl/db.Open (WAL, FK, busy timeout, 0600)
- db.Migrate: convert function-based migrations to mcdsl/db.Migration
  SQL strings, delegate to mcdsl/db.Migrate
- db.Snapshot: delegate to mcdsl/db.Snapshot (adds 0600 permissions)
- config: replace local Duration with mcdsl/config.Duration alias,
  replace Load with mcdsl/config.Load[T] + Validator interface
- Remove direct modernc.org/sqlite and go-toml/v2 dependencies
  (now indirect via mcdsl)
- Update TestEnvOverrideInvalidDuration: mcdsl silently ignores
  invalid env duration values (behavioral change from migration)
- All existing tests pass

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

go.mod

@@ -1,29 +1,32 @@
 module git.wntrmute.dev/kyle/mc-proxy
 
-go 1.25.0
+go 1.25.7
 
 require (
+	git.wntrmute.dev/kyle/mcdsl v0.0.0
 	github.com/oschwald/maxminddb-golang v1.13.1
-	github.com/pelletier/go-toml/v2 v2.2.4
 	github.com/spf13/cobra v1.10.2
-	google.golang.org/grpc v1.79.2
+	golang.org/x/net v0.48.0
+	google.golang.org/grpc v1.79.3
 	google.golang.org/protobuf v1.36.11
-	modernc.org/sqlite v1.46.2
 )
 
+replace git.wntrmute.dev/kyle/mcdsl => /home/kyle/src/metacircular/mcdsl
+
 require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/google/uuid v1.6.0 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/ncruces/go-strftime v1.0.0 // indirect
+	github.com/pelletier/go-toml/v2 v2.3.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
-	golang.org/x/net v0.48.0 // indirect
 	golang.org/x/sys v0.42.0 // indirect
 	golang.org/x/text v0.32.0 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20251202230838-ff82c1b0f217 // indirect
 	modernc.org/libc v1.70.0 // indirect
 	modernc.org/mathutil v1.7.1 // indirect
 	modernc.org/memory v1.11.0 // indirect
+	modernc.org/sqlite v1.47.0 // indirect
 )