feat(catalog): add channel management projection

[MrFr3di]

Scope

Stacked on #240. Adds the CC-2 hidden-aware Channel Management read projection without weakening normal browse semantics.

Planned contract:

• explicit management visibility modes: ALL, VISIBLE, HIDDEN;
• management rows expose canonical vs effective name/number, favorite, hidden state, and variant count;
• hidden rows remain excluded from normal ALL / FAVORITES / RECENT browse;
• management paging is Room-backed but does not perform EPG/NowNext enrichment;
• active source revisions only;
• one row per canonical channel across multiple provider variants;
• no Room schema/version change.

This PR starts RED-first: the first commit defines the API contract test before production implementation. It remains draft until exact-head checks are green.

[MrFr3di]

2026-09-01 restack analysis: treat this as the CC-2 incremental layer on top of rebuilt #240, not as its old 11-commit stack. None of CC-2's 11 changed files changed on current main after the #240 base, so the incremental CC-2 tree can also be carried byte-for-byte after CC-1. Requalify only the rebuilt exact head.