Add accessible captions and keyboard labels to Flask report tables

[Robinlee0929]

Context

The canonical Flask Reports page contains wide HA/VRRP and WireGuard evidence tables. Each table is inside a horizontal scroll container, but the tables have no <caption> and the scroll regions are not named or keyboard-focusable.

Adding these semantics will make the evidence easier to identify and navigate with assistive technology and keyboards.

Newcomer snapshot

• Difficulty: Beginner / Intermediate
• Scope: Small / Medium
• Primary area: Flask / Jinja HTML accessibility and pytest assertions
• Likely files: templates/dashboard_reports.html plus one or more of the existing focused dashboard test files
• Python required: Yes
• Node/npm required: No
• Physical hardware required: No
• Live device access required: No
• Credentials required: No
• External API/provider required: No
• Task-time network access required: No, after local dependencies are installed
• Start with: python -m pytest tests/test_dashboard_app.py tests/test_phase_2o_02_canonical_flask_overview_evidence_and_reports_visualization.py tests/test_phase_2o_03_canonical_flask_display_only_and_technical_detail_presentation.py
• Before completion: run the focused pytest command, full pytest, and python network_lab.py --task report-index
• Do not change: report discovery, report data, routes, filters, status normalization, command execution, network behavior, or live-device behavior

Dependency installation may require internet access; the access fields above describe the task after local prerequisites are installed.

Scope

Improve only the presentation semantics of the two existing tables in templates/dashboard_reports.html.

Do not change report discovery, report data, routes, filters, status normalization, or live/network behavior.

Acceptance criteria

• The HA/VRRP table has a concise, reviewer-facing <caption>.
• The WireGuard table has a concise, reviewer-facing <caption>.
• Each horizontal scroll container is exposed as a named region.
• Each scroll region can receive keyboard focus when horizontal scrolling is needed.
• Existing focus-visible styling remains usable for the new focus targets.
• Focused tests assert the captions and accessible region attributes.
• No new action controls, POST routes, report generation, or live-device behavior are added.

Suggested starting points

• templates/dashboard_reports.html
• templates/dashboard_base.html
• tests/test_dashboard_app.py
• tests/test_phase_2o_02_canonical_flask_overview_evidence_and_reports_visualization.py
• tests/test_phase_2o_03_canonical_flask_display_only_and_technical_detail_presentation.py

Validation

Run:

• python -m pytest tests/test_dashboard_app.py tests/test_phase_2o_02_canonical_flask_overview_evidence_and_reports_visualization.py tests/test_phase_2o_03_canonical_flask_display_only_and_technical_detail_presentation.py
• python -m pytest
• python network_lab.py --task report-index

Safety boundary

This change is limited to HTML semantics and tests. It must remain display-only and must not add report generation, command execution, SSH, network access, configuration changes, or live-device interaction.