chore(deps): migrate postgres driver from pgx v4 to v5

[AmanGIT07]

Summary

Migrates the Postgres driver from pgx v4 to pgx v5. The v4 line is in maintenance mode; v5 absorbed the standalone pgconn, pgproto3 and pgtype modules. Resolves the two govulncheck findings that have no fix on the v4 line (GO-2026-5004, GO-2026-4518). GO-2026-5617 is no longer reported as reachable once the v4 module family leaves the dependency graph.

Changes

• Swap github.com/jackc/pgx/v4 → github.com/jackc/pgx/v5: driver registration (stdlib) in cmd/serve.go and internal/store/postgres, pgx.ParseConfig in cmd/serve.go, pgx.Connect readiness probe in test/e2e/testbench
• Swap standalone github.com/jackc/pgconn → github.com/jackc/pgx/v5/pgconn for Postgres error inspection (postgres.go, billing_transactions_repository.go)
• go.mod: pgx/v5 v5.10.0 in; pgx/v4, pgconn, pgproto3/v2, pgtype, chunkreader/v2, pgio out
• Add TestCheckPostgresError covering every error-code translation in checkPostgresError, including wrapped errors and passthrough cases
• Add TestBillingTransactionRepository covering CreateEntry and replaying the same transaction (ErrAlreadyApplied)

Technical Details

No query or repository logic changes — the store layer talks to database/sql via goqu/sqlx, and the registered driver name stays pgx, so configuration is unchanged. Error matching relies on the driver returning v5's *pgconn.PgError; the new repository test exercises this against a real Postgres, including the constraint-name check in the billing replay path.

Base is chore/upgrade-go-deps (#1813); this PR retargets to main automatically when that merges.

Test Plan

• go build ./... and go vet ./... pass
• make lint passes (0 issues)
• make test passes (race detector, -count 2)
• make e2e-test passes against live Postgres + SpiceDB containers
• govulncheck ./... reports no findings from pgx modules

SQL Safety (if your PR touches *_repository.go or goqu.*)

• Values flow through ? placeholders, goqu.Ex{}, or goqu.Record{} — never fmt.Sprintf or + building a query that gets executed.
• ToSQL() callers capture and forward params (query, params, err := stmt.ToSQL(); db.…Context(ctx, …, query, params...)). Never query, _, err := ….
• No ? placeholders inside single-quoted SQL literals in goqu.L (use make_interval(hours => ?)-style functions instead).
• Any //nolint:forbidigo or // #nosec G20x annotation has a one-line justification on the same line that a reviewer can verify.

🤖 Generated with Claude Code

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Project	Deployment	Actions	Updated (UTC)
frontier	Ready	Preview, Comment	Jul 29, 2026 8:54am

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[coderabbitai]

🧹 Nitpick comments (1)

internal/store/postgres/billing_transactions_repository_test.go (1)

94-110: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Assert translated diagnostic details too.

The table cases populate only Code and assert ErrorIs. A regression that drops PgError.Detail or PgError.Message from the translated error would still pass. Add representative detail/message values and assert they are preserved.

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📥 Commits

Reviewing files that changed from the base of the PR and between 686bd6d and 41ecc3b.

⛔ Files ignored due to path filters (1)

• go.sum is excluded by !**/*.sum

📒 Files selected for processing (7)

• cmd/serve.go
• go.mod
• internal/store/postgres/billing_transactions_repository.go
• internal/store/postgres/billing_transactions_repository_pg_test.go
• internal/store/postgres/billing_transactions_repository_test.go
• internal/store/postgres/postgres.go
• test/e2e/testbench/postgres.go