Add DrizzleExtractor for Drizzle ORM schema files

[itsflaid]

Context
The slot is already reserved in extractors/index.ts (// new DrizzleExtractor()), documented as next in the fallback order right after Prisma.

Scope
Parse Drizzle schema files (pgTable / mysqlTable / sqliteTable calls, typically schema.ts or db/schema/*.ts) via ts-morph AST. Extract table name, columns as FieldInfo, relations from the relations() helper / references() foreign keys.

Acceptance criteria

• canHandle() detects Drizzle schema files (import from drizzle-orm)
• extract() returns fields with correct isRelation / isList / isOptional
• Registered above SQLExtractor, below PrismaExtractor
• source union extended with "drizzle"
• Tests added