feat: add usePrismaNames option to draw schema names instead of db names

[keonik]

Closes #128

What

Adds an opt-in usePrismaNames generator option. By default models and fields carrying @@map / @map are drawn with their database names; with this option they keep the names as written in the schema.

model User {
  id       Int    @id
  nickName String @map("nick_name")

  @@map("users")
}

usePrismaNames	Entity	Field
false (default)	users	nick_name
true	User	nickName

Covers models, composite types, enums and fields — per @michaelaltmann's note on the issue that this should apply to columns too.

Drive-by fix: @@maped enums rendered twice

While wiring this up, the entity-name resolution turned out to be inconsistent. The enum block rendered enum.dbName || enum.name, but the relationship line only searched models/composite types, never enums — so it fell through to the enum's Prisma name:

erDiagram
        roles {
            ADMIN ADMIN
            USER USER
        }
    "accounts" |o--|| "Role" : "enum:role"

Loading

Mermaid draws that as an extra empty Role node next to the populated roles one. Relationship endpoints now resolve through the same displayName helper the entity blocks use, so both say roles.

Output change for existing users

For schemas using @@map, relationship endpoints are now consistently quoted:

-    "profile" |o--|| users : "user"
+    "profile" |o--|| "users" : "user"

Mermaid parses both identically — this is the same node, just quoted like every other endpoint already was. Verified against prisma/mappings.prisma; the rest of the output is byte-identical.

Testing

• New __tests__/usePrismaNames.test.ts — both naming modes plus the enum-node regression. Renders to .md straight from the DMMF, so no browser needed.
• Full suite (30 files / 35 tests) passes against Prisma 7.
• Diffed generated output for prisma/mappings.prisma before/after to confirm the default path only changed in the two ways described above.