[pitill0]

Summary

Implements profile-scoped station provenance to track how stations enter a FluxTuner library without changing their shared station records or existing favorite metadata.

Changes

• Add SQLite schema v4 for station sources and source-to-station memberships.
• Support local_collection, remote_collection, and manual_entry provenance.
• Provide Core APIs for creating, listing, querying, and deleting profile-owned sources.
• Integrate provenance recording with GTK and TUI station imports and manual station creation.
• Integrate Web remote imports using persistent, single-use receipts bound to the authenticated user, profile, session, and exact downloaded content.
• Enforce receipt expiration and atomic consumption during import.
• Preserve existing station metadata, favorites, tags, and playlist relationships.
• Use opaque source references rather than storing source URLs or filesystem paths as provenance identifiers.

Security and compatibility

• Enforce profile ownership across provenance operations.
• Prevent remote-source attribution from unverified client claims.
• Reject expired, modified, cross-profile, cross-user, or reused remote import receipts.
• Preserve rollback behavior when imports fail.
• Keep existing import response contracts compatible.

Scope

• The Web API supports explicitly selected profiles.
• The current Web interface operates on the default profile; a graphical profile selector is outside this PR.
• Full profile-management UX for GTK/TUI/Web is outside this PR.

Validation

• Full suite: 1,672 passed, 8 skipped.
• Ruff: passed.
• Ruff format: passed for all 25 changed/new Python files.
• Mypy: passed for the six checked modules.
• JavaScript syntax checks: passed.
• git diff --check: passed.

Closes #276.