Streamline PR, Merge & Deploy Workflows

[ccampbell-fearless]

Description

There is overlap between what runs on PR checks and what runs on merge to main resulting in duplicate job execution. Additionally, the backend and terraform deployments are coupled in a way that causes unnecessary runs when only one area has changed. This ticket consolidates and decouples these workflows.

Tasks

• Consolidate duplicate jobs between PR checks and merge to main workflows.
• Suppress application tests when source code has not changed (for example, updates to docs/ or .github/ should not trigger tests)
• Suppress terraform applies when terraform has not changed
• Suppress app deployments when source code has not changed