docs: clarify cert mapping, onboarding prompt details, and Android zipalign step

[Lash-L]

Description

This PR incorporates user feedback and clarifies several common setup pitfalls noted in #59 (comment):

1. Custom TLS / Docker path mapping (docs/custom_cert_management.md & docs/installation.md):

   • Clarified that paths in config.toml are evaluated inside the container.
   • Explained that ./data on the host maps to /data in the container (so host files placed in ./data/certs/ correspond to /data/certs/... in config.toml).
   • Added guidance on troubleshooting FileNotFoundError (inspecting docker compose logs) if host-absolute paths are unmounted, and how to mount external host cert directories in compose.yaml.

2. Onboarding prompts & Country Domain (docs/onboarding.md):

   • Documented the prompts in the CLI/GUI flow, specifically explaining cst and country-domain.
   • Added a dedicated section explaining --country-domain: how auto-detection works for built-in timezones, what happens for unlisted timezones (e.g. Europe/Vienna), and valid input values (2-letter ISO country codes or regional codes like eu/us).
   • Added Central Europe (Vienna / CET) to the CST examples table (CET-1CEST,M3.5.0,M10.5.0/3).

3. Android APK Alignment (docs/roborock_app.md):

   • Added zipalign to the prerequisites list.
   • Inserted a required zipalign -p -f 4 step before �pksigner sign to satisfy Android 11+ (API 30+) 4-byte/page-alignment requirements for uncompressed native libraries (librrcodec.so), resolving INSTALL_FAILED_INVALID_APK (res=-124) during �db install.

4. Compatibility list (docs/tested_vacuums.md):

   • Linked #59 as an additional confirmation report for QRevo Edge 2 Set (a298).

Verification

• uv run mkdocs build --strict succeeded with 0 warnings or errors.