Updated Readme files

pkg/writers/dbml/README.md

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+# DBML Writer
+
+Generates Database Markup Language (DBML) files from database schema information.
+
+## Overview
+
+The DBML Writer converts RelSpec's internal database model representation into DBML syntax, suitable for use with dbdiagram.io and other DBML-compatible tools.
+
+## Features
+
+- Generates DBML syntax
+- Creates table definitions with columns
+- Defines relationships
+- Includes indexes
+- Adds notes and documentation
+- Supports enums
+
+## Usage
+
+### Basic Example
+
+```go
+package main
+
+import (
+    "git.warky.dev/wdevs/relspecgo/pkg/models"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers"
+    "git.warky.dev/wdevs/relspecgo/pkg/writers/dbml"
+)
+
+func main() {
+    options := &writers.WriterOptions{
+        OutputPath: "schema.dbml",
+    }
+
+    writer := dbml.NewWriter(options)
+    err := writer.WriteDatabase(db)
+    if err != nil {
+        panic(err)
+    }
+}
+```
+
+### CLI Examples
+
+```bash
+# Generate DBML from PostgreSQL database
+relspec --input pgsql \
+  --conn "postgres://localhost/mydb" \
+  --output dbml \
+  --out-file schema.dbml
+
+# Convert GORM models to DBML
+relspec --input gorm --in-file models.go --output dbml --out-file database.dbml
+
+# Convert JSON to DBML for visualization
+relspec --input json --in-file schema.json --output dbml --out-file diagram.dbml
+```
+
+## Generated DBML Example
+
+```dbml
+Project MyDatabase {
+  database_type: 'PostgreSQL'
+}
+
+Table users {
+  id bigserial [pk, increment]
+  username varchar(50) [not null, unique]
+  email varchar(100) [not null]
+  bio text [null]
+  created_at timestamp [not null, default: `now()`]
+
+  Note: 'Users table'
+
+  indexes {
+    email [name: 'idx_users_email']
+  }
+}
+
+Table posts {
+  id bigserial [pk, increment]
+  user_id bigint [not null]
+  title varchar(200) [not null]
+  content text [null]
+  created_at timestamp [default: `now()`]
+
+  indexes {
+    user_id [name: 'idx_posts_user_id']
+    (user_id, created_at) [name: 'idx_posts_user_created']
+  }
+}
+
+Ref: posts.user_id > users.id [delete: cascade, update: no action]
+```
+
+## DBML Features
+
+### Table Definitions
+```dbml
+Table table_name {
+  column_name type [attributes]
+}
+```
+
+### Column Attributes
+- `pk` - Primary key
+- `increment` - Auto-increment
+- `not null` - NOT NULL constraint
+- `null` - Nullable (explicit)
+- `unique` - Unique constraint
+- `default: value` - Default value
+- `note: 'text'` - Column note
+
+### Relationships
+```dbml
+Ref: table1.column > table2.column
+Ref: table1.column < table2.column
+Ref: table1.column - table2.column
+```
+
+Relationship types:
+- `>` - Many-to-one
+- `<` - One-to-many
+- `-` - One-to-one
+
+Relationship actions:
+```dbml
+Ref: posts.user_id > users.id [delete: cascade, update: restrict]
+```
+
+### Indexes
+```dbml
+indexes {
+  column_name
+  (column1, column2) [name: 'idx_name', unique]
+}
+```
+
+## Type Mapping
+
+| SQL Type | DBML Type |
+|----------|-----------|
+| bigint | bigint |
+| integer | int |
+| varchar(n) | varchar(n) |
+| text | text |
+| boolean | boolean |
+| timestamp | timestamp |
+| date | date |
+| json | json |
+| uuid | uuid |
+
+## Notes
+
+- DBML is designed for database visualization
+- Can be imported into dbdiagram.io
+- Human-readable format
+- Schema names can be included in table names
+- Comments and notes are preserved
+- Ideal for documentation and sharing designs