chore: remove dead code from pre-nixpacks step pipeline

[Alimedhat000]

Context

After merging #12 (nixpacks build pack), the old manual step-based static build pipeline is no longer used. Files are marked with `// DEAD CODE: Replaced by Nixpacks strategy (nixpacks.ts). Remove after #12 stable.`

Files to delete

Path	Reason
`packages/worker/src/deployments/strategies/static.ts`	Replaced by nixpacks static path
`packages/worker/src/deployments/steps/clone-step.ts`	Nixpacks handles cloning
`packages/worker/src/deployments/steps/install-step.ts`	Nixpacks handles install
`packages/worker/src/deployments/steps/build-step.ts`	Nixpacks handles build
`packages/worker/src/deployments/steps/verify-step.ts`	Nixpacks handles output
`packages/worker/src/deployments/steps/copy-step.ts`	Nixpacks handles file serving
`packages/worker/src/deployments/errors/classify-error.ts`	Only used by old step files
`packages/worker/test/unit/deployments/classify-error.test.ts`	Tests for deleted error classifier
`packages/worker/test/unit/deployments/steps/verify-step.test.ts`	Tests for deleted verify step

Notes

• No other files import from these — confirmed via `rg` search
• `pipeline.ts` only imports from nixpacks and dockerfile strategies now
• Wait until nixpacks has been running in prod for a week or two before merging