fix: escape backticks in generated Go struct tags

[Kjubikstronk]

Closes #1125.

The Go generator writes struct tags as a raw string literal, ```go
json:"NAME"

and Go raw literals cannot contain a backtick at all. A column named `bad`tag` therefore closes the literal early and the generated file is not parseable Go, so `gofmt` reports "string literal not terminated".

Go allows a struct tag to be an interpreted literal too, so this switches to that form only when the tag contains a backtick, escaping backslashes and double quotes. Names without a backtick keep the exact raw-literal output they had before, which is what the issue asks for.

There were two identical call sites, one for tables and views and one for composite types. Both now go through the same helper.

Three tests added to the existing `test/server/templates/go.test.ts`, which is a pure unit test file needing no database: a backtick name produces the escaped interpreted literal, a name with a double quote and a backtick escapes both, and an ordinary name still produces the unchanged raw literal. The first two fail without the change and the third passes either way, so the previous output is pinned as well.

`prettier --check` and `tsc -p tsconfig.json --noEmit` are clean.

[spydon]

Thank you for the contribution! postgres-meta's type generation is moving to the shared @supabase/postgrest-typegen package in supabase/sdk (see #1084), so open template fixes are being re-landed there. The struct tag escaping issue this PR addresses is fixed in supabase/sdk#122, which also escapes quotes, backslashes and control characters inside the tag value so reflect.StructTag.Get round-trips the exact column name.

[Kjubikstronk]

Makes sense, and sdk#122 is the better fix, since escaping quotes, backslashes and control characters means reflect.StructTag.Get round-trips anything rather than just surviving a backtick. Closing this one. I had not spotted #1084, so thanks for the pointer.