refactor: split architecture rules into domain-specific files

Split the monolithic .architecture-rules.yaml (1700+ lines) into focused
domain-specific files in .architecture-rules/ directory:

- _main.yaml: Core config, principles, ignore patterns, severity levels
- api.yaml: API endpoint rules (API-001 to API-005)
- service.yaml: Service layer rules (SVC-001 to SVC-007)
- model.yaml: Model rules (MDL-001 to MDL-004)
- exception.yaml: Exception handling rules (EXC-001 to EXC-005)
- naming.yaml: Naming convention rules (NAM-001 to NAM-005)
- auth.yaml: Auth and multi-tenancy rules (AUTH-*, MT-*)
- middleware.yaml: Middleware rules (MDW-001 to MDW-002)
- frontend.yaml: Frontend rules (JS-*, TPL-*, FE-*, CSS-*)
- language.yaml: Language/i18n rules (LANG-001 to LANG-010)
- quality.yaml: Code quality rules (QUAL-001 to QUAL-003)

Also creates scripts/validators/ module with base classes for future
modular validator extraction.

The validate_architecture.py loader now auto-detects and merges split
YAML files while maintaining backward compatibility with single file mode.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.architecture-rules/model.yaml

@@ -0,0 +1,55 @@
+# Architecture Rules - Model Rules
+# Rules for models/database/*.py and models/schema/*.py files
+
+model_rules:
+
+  - id: "MDL-001"
+    name: "Database models must use SQLAlchemy Base"
+    severity: "error"
+    description: |
+      All database models must inherit from SQLAlchemy Base and use proper
+      column definitions with types and constraints.
+    pattern:
+      file_pattern: "models/database/**/*.py"
+      required_patterns:
+        - "class.*\\(Base\\):"
+
+  - id: "MDL-002"
+    name: "Use Pydantic models separately from SQLAlchemy models"
+    severity: "error"
+    description: |
+      Never mix SQLAlchemy and Pydantic in the same model.
+      SQLAlchemy = database schema, Pydantic = API validation/serialization.
+    pattern:
+      file_pattern: "models/**/*.py"
+      anti_patterns:
+        - "class.*\\(Base, BaseModel\\):"
+
+  - id: "MDL-003"
+    name: "Pydantic models must use from_attributes for ORM mode"
+    severity: "error"
+    description: |
+      Pydantic response models must enable from_attributes to work with SQLAlchemy models.
+    pattern:
+      file_pattern: "models/schema/**/*.py"
+      required_in_response_models:
+        - "from_attributes = True"
+
+  - id: "MDL-004"
+    name: "Database tables use plural names"
+    severity: "warning"
+    description: |
+      Database table names should be plural lowercase following industry standard
+      conventions (Rails, Django, Laravel, most ORMs). A table represents a
+      collection of entities, so plural names are natural: 'users', 'orders',
+      'products'. This reads naturally in SQL: SELECT * FROM users WHERE id = 1.
+
+      Examples:
+        - Good: users, vendors, products, orders, order_items, cart_items
+        - Bad: user, vendor, product, order
+
+      Junction/join tables use both entity names in plural:
+        - Good: vendor_users, order_items, product_translations
+    pattern:
+      file_pattern: "models/database/**/*.py"
+      check: "table_naming_plural"