Release 0.6.0-dev: stabilize profiles workspace and locale bootstrap

[Goudron]

Summary

This PR merges dev into main for 0.6.0-dev.

The release focuses on stabilizing the Profiles workspace after recent UI and bootstrap regressions. It restores reliable first-load behavior, fixes locale and theme initialization, improves the profile library layout, and closes several workflow bugs across the guided and advanced editing paths.

What changed

• stabilized client bootstrap for the Profiles page
• fixed cold-start locale loading for dynamic UI labels and actions
• restored reliable language and theme switching
• reworked the profile library into a wider table-style layout
• fixed profile open state, lifecycle visibility, and final review/export rendering
• fixed empty shareable summary and copy behavior on step 8
• improved dark theme coverage and contrast in remaining problem areas
• normalized the working database setup around a single active DB
• rebuilt the default library to contain only the two intended starter profiles
• fixed profile search behavior and protected production data from test pollution
• updated tests to cover the new locale bootstrap contract

Validation

• verified the Profiles page in live Chromium, including cold reload scenarios
• verified locale-sensitive UI on first load and after opening a profile
• ran targeted frontend and service tests during each fix cycle
• final checks passed with full application coverage

Test commands

./.venv/bin/pytest --cov=app --cov-report=term-missing -q
./.venv/bin/python -m mypy app