Modernization roadmap: stabilize and refactor range-api in phased deliveries

## Goal
Deliver a phased modernization of `range-api` to reduce operational risk, improve maintainability, and increase delivery velocity without disrupting current behavior.

## Scope
This roadmap is organized into quick wins, short projects, and longer initiatives based on impact/risk reduction.

## Outcomes
- Safer runtime behavior (error handling + startup semantics)
- CI/runtime consistency and more reliable signals
- Better module boundaries (controller -> service -> repository)
- Stronger typing in critical paths
- Predictable configuration and test execution

## Sub-tasks
- [ ] #524 Quick wins: runtime stability, CI alignment, and config/test hygiene
- [ ] #525 Extract plan vertical slice to controller/service/repository boundary
- [ ] #526 Replace DataManager dynamic usage with explicit dependencies
- [ ] #527 Decompose auth middleware responsibilities
- [ ] #528 Centralize and type environment configuration
- [ ] #529 TypeScript hardening for runtime-critical path
- [ ] #530 Reduce any usage in db2 model/query layer

## Suggested order
1. #524
2. #525
3. #526
4. #527
5. #528
6. #529
7. #530

## Definition of done
- Child tasks are completed and merged to `dev`
- CI passes on target Node version
- No startup/error-path regressions in API behavior
- Documentation reflects current runtime/toolchain