feat: adds Flyway database migration tooling

[rahulvikram]

This PR:

• Adds Flyway community database migration tooling to docker-compose startup process
• Adds notes to documentation about database setup and migration for development
• Removes old db-init.sql
• Migration: adds altText to Items and History_Items

[Copilot]

Pull request overview

Adds Flyway Community database migration support to the Docker Compose dev workflow and documents how schema changes should be managed going forward, including an initial migration to add altText columns for accessibility.

Changes:

• Introduces a flyway Docker Compose service that runs migrations after MariaDB is healthy and before the app starts.
• Adds developer documentation for migration naming, safety, and running Flyway commands via Docker Compose.
• Adds V001 migration to add altText columns to Items and History_Items.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
services/database/migrations/V001__add_altText_to_Items_and_History_Items.sql	Adds initial schema migration for altText columns.
services/database/migrations/README.md	Documents Flyway migration conventions and usage.
README.md	Updates dev DB guidance to Docker Compose + Flyway and fixes env var naming.
DOCKER.md	Documents Flyway service behavior and migration commands in Docker workflow.
docker-compose.yml	Adds Flyway service and gates app startup on successful migrations.
CONTRIBUTING.md	Updates contributor workflow to use the new seed and migration process.

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