feat: add db migration tool

[mattjohnsonpint]

Adds a db migration tool, useful when installing Modus into a production environment other than Hypermode.

Note that the migration scripts are physical copies because go embed doesn't allow parent directories or symlinks.

[Copilot]

Pull Request Overview

This PR adds a database migration tool to support installing Modus into production environments other than Hypermode. The tool embeds SQL migration scripts and provides a simple Go-based utility to apply database schema changes to PostgreSQL databases.

Key changes:

• Creates a standalone Go tool for database migrations with embedded SQL scripts
• Adds physical copies of migration scripts due to go embed limitations with parent directories
• Integrates the migration tool into the build process to keep scripts synchronized

Reviewed Changes

Copilot reviewed 20 out of 21 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tools/modus-dbmigrate/main.go	Core migration tool implementation with embedded filesystem and database connection handling
tools/modus-dbmigrate/go.mod	Go module definition specifying Go 1.25.0 and migration dependencies
tools/modus-dbmigrate/README.md	Documentation for installation and usage of the migration tool
tools/modus-dbmigrate/migrations/*.sql	Physical copies of database migration scripts for embedding
runtime/Makefile	Build process integration to copy migration scripts from runtime to tool directory
go.work	Workspace configuration to include the new migration tool module

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