feat(core): tenant-scoped PostgresLibraryRepository (Phase 1.b.5a)

[InstaZDLL]

Summary

Phase 1.b.5a — give `waveflow-server` the tenant-scoped surface for the second resource family (library). Same shape as PRs #181 / #183 / #184 for profile.

Strategy

`PostgresLibraryRepository` carries inherent methods only — does not implement `LibraryRepository`. The trait is single-tenant (no `user_id` parameter); exposing it on a multi-tenant Postgres backend would let a careless caller bypass the user_id filter.

Every method takes both `profile_id` (the owning profile) AND `user_id` (the authenticated user). The SQL encodes the ownership pair (`library.profile_id` ↔ `profile.user_id`) in its WHERE clause, so storage is the single point of enforcement — no convention-by-comment.

Method	Pattern
`list_for_profile`	`WHERE profile_id = $1 AND EXISTS (… p.user_id = $2)` — empty list for non-owner
`get_for_profile`	same `EXISTS`, `Option`
`insert_for_profile`	`INSERT … SELECT FROM profile WHERE id = $1 AND user_id = $7 RETURNING *`
`update_for_profile`	`UPDATE … COALESCE … RETURNING *` (same race-free pattern as PR #184's rename)
`delete_for_profile`	`DELETE … WHERE … AND EXISTS (…)`, `Ok(bool)` for "row removed?"

Domain

`Library` gains `profile_id: i64` with `#[sqlx(default)]` — mirrors how `Profile.user_id` round-trips on the desktop SQLite that has no column for it. The lone desktop call site (`commands/library::create_library`) sets `profile_id: 0` explicitly.

Counts (`track_count`, `album_count`, …) are stubbed at `0::bigint` in every SELECT — they become real aggregates as tracks / playlists land in 1.b.5b+, without changing the wire shape.

Out of scope

• The `library` schema migration — lives in `waveflow-server/migrations/` (next PR 1.b.5a-PR-B).
• Folder management methods (`list_folders`, `insert_folder`, etc.) — the desktop's scan path uses them; the server doesn't need them yet.
• Track / playlist Postgres repositories — 1.b.5b / 1.b.5c.

Test plan

• `cargo check --workspace --all-targets` ✅
• `cargo clippy --workspace --all-targets -- -D warnings` ✅
• `cargo test --workspace` ✅ (66 + 45 = 111 tests pass, zero regression)
• PR B on waveflow-server consumes this via git dep and exercises every `*_for_profile` method through the `/api/v1/profiles/{profile_id}/libraries` CRUD endpoints + Postgres service container.

Summary by CodeRabbit

Chores

• Améliorations internes de l'infrastructure de gestion des bibliothèques et support PostgreSQL.

[coderabbitai]

📝 Walkthrough

Walkthrough

Ce PR ajoute un modèle de tenancy multi-tenant à la structure Library. Le champ profile_id est ajouté à la DTO, un dépôt PostgreSQL complet avec sécurité tenant-scoped (validant profile_id et user_id dans chaque opération SQL) est implémenté, et la commande single-tenant est mise à jour pour définir la sentinelle profile_id: 0.

Changes

Tenancy Model et Repository Postgres Tenant-Scoped

Layer / File(s)	Summary
Domain model with profile_id field src-tauri/crates/core/src/domain/library.rs	Library DTO ajoute profile_id: i64 documenté pour SQLite (0) et Postgres (> 0), avec #[sqlx(default)] conditionnels pour mapper les requêtes sans sélection explicite.
PostgreSQL tenant-scoped repository with CRUD operations src-tauri/crates/core/src/repository/postgres/library.rs, src-tauri/crates/core/src/repository/postgres/mod.rs	PostgresLibraryRepository implémente list_for_profile, get_for_profile, insert_for_profile, update_for_profile, delete_for_profile avec contrainte tenant profile_id + user_id appliquée via EXISTS dans chaque requête SQL. Les compteurs sont projetés à 0. Module exports ajoutés pour PostgresLibraryRepository.
Command layer single-tenant sentinel src-tauri/crates/app/src/commands/library.rs	create_library construit explicitement le retour Library avec profile_id: 0, documentant le modèle single-tenant et la cohérence du round-trip.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• InstaZDLL/WaveFlow#181: Modifie Library pour SQLx en Postgres (dérivation FromRow dans le PR référencé vs. ajout du champ profile_id persisté dans ce PR), dépendance DTO directe.

Suggested labels

type: feat, size: xl, scope: backend

Poem

🏢 Les profils s'enferment dans leur profile_id
Postgres valide chaque accès tenant
Single ou multi, la sentinelle guide le flux
Compteurs à zéro, sécurité garantie
WaveFlow prend forme, ligne par ligne ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	Le titre suit la convention Conventional Commits avec le scope « core » et décrit précisément l'ajout du PostgresLibraryRepository tenant-scoped, correspondant au changement principal du PR.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	La description respecte la structure du template : titre en Conventional Commits, résumé clair, stratégie détaillée avec table des patterns SQL, domaine expliqué, périmètre délimité, et plan de test complet.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/core-tenant-library-postgres

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