Fix Postgres placeholder rewrite to preserve sqlc numbered placeholders

[DeveloperDurp]

Motivation

• The PostgreSQL driver rewrite mangled sqlc/SQLite numbered placeholders (e.g. ?1 -> $11) causing prepared statements to refer to non-existent parameters and producing runtime query errors.

Description

• Updated internal/pgdriver/rewrite.go so the placeholder rewriter consumes digits after ? and preserves numbered placeholders (e.g. ?1 -> $1) while still renumbering anonymous ? placeholders to $1, $2, ....
• The rewriter now advances its internal counter to the highest explicit numbered index seen so that subsequent anonymous placeholders continue at the correct numbering.
• Kept existing literal handling so ? occurrences inside single- or double-quoted strings remain untouched.
• Added regression tests in internal/pgdriver/rewrite_test.go covering repeated numbered placeholders, mixed numbered/anonymous placeholders, and numbered placeholders inside string literals.

Testing

• Ran go test -count=1 ./internal/pgdriver and the package tests passed successfully.
• Ran gofmt checks and git diff --check to ensure formatting and basic checks passed with no reported issues.
• Ran go test -count=1 ./..., which exercised many packages successfully but failed to complete because generated templ files and static/swagger-ui assets required by the top-level build/tests were not present in this checkout; this is a known repository precondition and unrelated to the placeholder fix.

---

Codex Task