fix: classify duplicate-key Insert as record.IsAlreadyExists

[trakhimenok]

Summary

• Bump dal-go/dalgo2sql to v0.11.0 (adds the DbOptions.IsAlreadyExists classifier hook), dal-go/dalgo to v0.66.1 (adds the now-passing unconditional dalgotest conformance check), and dal-go/record to v0.1.3 (adds ErrRecordExists/IsAlreadyExists).
• Add IsAlreadyExists, this adapter's classifier for modernc.org/sqlite (the driver this repo actually uses — confirmed via go.mod, no mattn/go-sqlite3 dependency). It matches errors.As(err, *sqlite.Error) against the extended result codes SQLITE_CONSTRAINT_PRIMARYKEY (1555) and SQLITE_CONSTRAINT_UNIQUE (2067) — never on message text. Both codes are matched deliberately: a duplicate primary key reports 1555, not 2067, and is the commonest case (this repo's own conformance suite exercises exactly that path). The primary result code SQLITE_CONSTRAINT (19) is deliberately not matched, since it also covers NOT NULL/CHECK/FOREIGN KEY violations.
• Wire it into NewDatabaseWithOptions as the default whenever the caller-supplied DbOptions.IsAlreadyExists is nil, so NewDatabase and every existing caller (including this package's own TestConformance) get classification with zero extra configuration, while still allowing an explicit override.
• Exported (dalgo2sqlite.IsAlreadyExists) so a caller assembling a custom DbOptions can reuse or compose with it.

Verification

• Cross-checked both constants against modernc.org/sqlite@v1.57.0's lib/sqlite.go, and confirmed the driver enables extended result codes on every connection it opens (conn.go's open() calls sqlite3_extended_result_codes(db, 1) unconditionally), so (*sqlite.Error).Code() reports the extended code, not the primary one.
• Confirmed the wiring is load-bearing: temporarily reverting the NewDatabaseWithOptions default made TestConformance/rejects_an_Insert_over_an_existing_key_with_record.IsAlreadyExists fail with the driver reporting exactly extended code 1555.
• New sqlite_classifier_test.go drives a real in-memory modernc.org/sqlite database (not hand-built error structs, since sqlite.Error's fields are unexported) to prove: a duplicate primary key is classified, a duplicate unique-index value is classified, and a NOT NULL violation and a CHECK violation are each not classified.
• go build ./..., go vet ./..., gofmt -l . (clean), golangci-lint run ./... (0 issues), and go test -race ./... all pass, including the shared dalgotest conformance suite (SQLite is in-process, so it runs for real here — no env-gate, no skip).

Test plan

• go build ./...
• go vet ./...
• gofmt -l .
• golangci-lint run ./...
• go test -race ./... (including TestConformance)
• CI green on the PR

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