[Part 1 / Phase 6] PathogenTestForm: Create TubeFieldHandler

[roldy]

Problem Description

Context

Part of Epic: [Epic] PathogenTestForm: Composition + Stable Form Refactor
Blocked by: Phase 5

The tube pair (tube count + tube description) listener pattern is duplicated 4× across
PathogenTestForm. Extract into a standalone TubeFieldHandler (~80 lines) with no
dependency on PathogenTestForm.

Proposed Solution

Tasks

• Create TubeFieldHandler.java
• Wire TuberculosisDiseaseSectionLayout to use TubeFieldHandler (replace Phase 3 stub)
• Remove now-redundant tube helper methods from PathogenTestForm

Additional Information

Acceptance Criteria

• TubeFieldHandler has no reference to PathogenTestForm
• Tube show/hide behavior on test type change is identical to before
• mvn compile -pl sormas-ui passes