docs: fix doc paths left stale by the docs restructure

[Gabeyocum28]

What does this PR do?

Repoints every user-facing reference to a flat docs/*.md guide that no longer exists at that path:

Old path	Now at	Referenced from
docs/raspberry-pi-setup.md	docs/setup/raspberry-pi.md	hardware-help issue template, scripts/setup/setup.sh, setup_kld7_devices.sh, capture_kld7_radc.py
docs/sound-trigger-wiring.md	docs/build/sound-trigger.md	hardware-help issue template, link text in CLAUDE.md / AGENTS.md
docs/kld7-troubleshooting.md	docs/legacy/troubleshooting.md	hardware-help issue template
docs/cloud-sync.md	docs/using/cloud-sync.md	scripts/setup/setup.sh
docs/spin-dechirp-replay.md	docs/development/spin-replay.md	scripts/analysis/replay_spin_dechirp.py docstring
docs/yolo-performance-tuning.md	docs/development/camera-yolo.md	scripts/vision/test_yolo_detection.py

Two section pointers in setup.sh ("→ Radar Setup", "(K-LD7 Angle Radar Setup)") were updated to headings that exist in the new page ("→ Troubleshooting", "(K-LD7 Device Names)"). Changelog entry added under Unreleased / Fixed.

Intentionally left alone: one warning string in src/openflight/kld7/radc.py that names docs/kld7-troubleshooting.md. Fixing it would make this a src/ change; it can ride along with the next K-LD7 code PR.

Why was this required?

The docs restructure (45d3b4d) moved these guides into sectioned directories but did not update the places outside docs/ that point at them. The hardware-help issue template's three "check these first" links have returned 404 since, and setup.sh, the script README tells every new builder to run, prints "see docs/raspberry-pi-setup.md" in its failure and skip messages, sending users to a file that isn't there.

Automated tests

None added. The change is confined to an issue-template YAML, string literals in shell and Python scripts under scripts/, Markdown link text, and the changelog. No code under src/openflight/ or ui/src/ is touched, so there is no behavior to test. Suggest the no-tests-needed label.

Manual (human) testing

• Confirmed via git log --follow that all six old files were deleted in the restructure commit 45d3b4d, and confirmed each successor page by reading its heading (e.g. docs/legacy/troubleshooting.md is titled "K-LD7 Troubleshooting Guide", docs/development/spin-replay.md is the reference for replay_spin_dechirp.py).
• Fetched each issue-template link from GitHub with curl: all three old blob/main URLs return 404, all three new ones return 200.
• Confirmed the two referenced section headings ("Troubleshooting", "K-LD7 Device Names", plus the pre-existing "Auto-Start on Boot") exist in docs/setup/raspberry-pi.md.
• Scanned every docs/…​.md path mentioned under scripts/, .github/, README, CONTRIBUTING, CLAUDE.md, AGENTS.md and ui/README.md against the filesystem: zero missing targets remain.
• bash -n on both shell scripts, py_compile on all three Python scripts, and yaml.safe_load on the template all succeed.
• uv run pytest tests/test_geekworm_setup.py tests/test_desktop_launcher.py tests/test_openflight_service.py tests/test_project_metadata.py: 21 passed.

No UI changes, so no screenshots.

Checklist

• Single feature/fix — this PR is scoped to one thing with a clear story above
• Automated tests included — not applicable, docs/scripts strings only (see above)
• Manual testing described — I documented what I verified by hand above
• Python tests pass (uv run pytest tests/ -v) — no Python package code changed
• Pylint passes (uv run pylint src/openflight/ --fail-under=9) — no src/ changes
• Ruff passes (uv run ruff check src/openflight/) — no src/ changes
• UI builds (cd ui && npm run build) — no UI changes
• UI lint passes (cd ui && npm run lint) — no UI changes
• Updated docs or CHANGELOG if needed
• No unrelated changes mixed in