docs: add CLAUDE.md for Claude Code integration

.gitignore

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 .idea
+.claude
 /release
 coverage.txt

CLAUDE.md

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+# authz_client
+
+Shared Go library for authorization service client integration.
+
+## Shared Documentation
+
+@../docs/claude/architecture.md
+@../docs/claude/go-services.md
+@../docs/claude/conventions.md
+
+## Library Information
+
+### Purpose
+
+Provides a client for the authz-service, handling privilege management for users across companies. Used by all microservices that need to check user permissions.
+
+### Usage
+
+```go
+import client "gitlab.com/unboundsoftware/shiny/authz_client"
+
+// Create handler with options
+handler := client.New(client.WithBaseURL("http://authz-service"))
+
+// Check user privileges
+privileges := handler.Get(email, companyID)
+if privileges.Invoicing {
+    // User has invoicing privileges
+}
+```
+
+### Privileges
+
+The `CompanyPrivileges` struct contains permission flags:
+- `Admin` - Administrative access
+- `Company` - Company management
+- `Consumer` - Consumer/customer access
+- `Time` - Time tracking
+- `Invoicing` - Invoice management
+- `Accounting` - Accounting access
+- `Supplier` - Supplier management
+- `Salary` - Salary/payroll access
+
+### Event Handling
+
+Implements `goamqp` message handlers to receive privilege update events from the authz-service, keeping the local privilege cache up-to-date.