[Modifications] Unify the two test directory conventions (`src/__tests__/` and `tests/`)

[RUKAYAT-CODER]

Overview

Tests live under two roots — src/__tests__/ and tests/ — plus colocated __tests__ directories inside src/components/ and src/services/, plus a _tests_ directory (single underscores) under src/components/dashboard/ that eslint.config.js explicitly ignores, plus two stray test files in report/ that Jest never picks up. Several modules have tests in both roots: axios.config.test.ts exists at src/__tests__/services/api/, tests/, and tests/services/api/ — three copies. This makes it impossible to know whether a module is tested without searching four locations.

Specifications

Features:

• One test-location convention, documented
• Duplicate test files merged
• The _tests_ directory renamed and un-ignored

Tasks:

• Choose colocated __tests__ or a top-level tests/ mirror and document the decision
• Merge the three axios.config.test.ts copies and any other duplicates
• Rename src/components/dashboard/_tests_/ and remove the ESLint ignore
• Move or delete the stray tests in report/
• Update jest.config.js roots and CONTRIBUTING.md

Impacted Files:

• src/__tests__/
• tests/
• src/components/dashboard/_tests_/
• report/
• jest.config.js
• CONTRIBUTING.md

Acceptance Criteria

• Tests live in one documented location
• No module has tests in two places
• Every test file is inside a Jest root