feat: indexers and download clients you add and configure (M502 #5518)

Admin → Integrations gains "Indexers and download clients": two lists of
connections the operator adds, Fabled Librarian's model. Nothing is seeded
or copied from Lidarr.

- Indexers: Prowlarr (its native /api/v1/search, which asks every indexer
  at once; Prowlarr has no aggregate Torznab feed) and any Torznab feed.
- Download clients: qBittorrent (WebUI v2, with re-login on an expired
  session) and FabledExchange, one entry with a switch per job:
  downloads (/api/downloads), search (/api/search) and release details
  (/api/torrents/{infohash}). All three start on; its key is optional.
- Each entry: enable, name, address, a write-only key or password, Test.
  A download client's Test lists its torrents and checks the downloads
  folder is visible and writable from Minstrel; an Exchange's Test
  reports each job switched on.
- Download clients carry a path mapping (Minstrel's /downloads vs the
  client's own name for it); search sources carry searches per hour.

Migration 0079 adds acquisition_services with its CHECKs. Ported from
Fabled Librarian: internal/indexer (Torznab, 429 Retry-After, magnet
redirects), internal/prowlarr, internal/exchange, internal/downloader,
and internal/acquire's one builder per kind, which Test already uses
so a passing Test vouches for the path a grab will take.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/api.go

@@ -13,6 +13,7 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 
+	"git.fabledsword.com/bvandeusen/minstrel/internal/acquire"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/auth"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/config"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/coverart"
@@ -70,6 +71,7 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 		fingerprintSettings: fpSettings,
 		loudnessSettings:    loudSettings,
 		acoustIDLookup:      acoustIDLookup,
+		acquisition:         acquire.NewStore(pool),
 		leveled:             newLeveledRenderer(dataDir, loudSettings, logger),
 		librarySize:         recommendation.NewLibrarySize(nil),
 		loginGuard:          auth.NewLoginGuard(),
@@ -214,6 +216,15 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 				admin.Get("/lidarr/config", h.handleGetLidarrConfig)
 				admin.Put("/lidarr/config", h.handlePutLidarrConfig)
 				admin.Post("/lidarr/test", h.handleTestLidarrConnection)
+				admin.Get("/acquisition/services", h.handleListAcquisitionServices)
+				admin.Post("/acquisition/services", h.handleCreateAcquisitionService)
+				admin.Put("/acquisition/services/{code}", h.handleUpdateAcquisitionService)
+				admin.Delete("/acquisition/services/{code}", h.handleDeleteAcquisitionService)
+				admin.Post("/acquisition/services/{code}/test", h.handleTestAcquisitionService)
+				admin.Put("/acquisition/services/{code}/api-key", h.handleSetAcquisitionSecret("api_key"))
+				admin.Delete("/acquisition/services/{code}/api-key", h.handleSetAcquisitionSecret("api_key"))
+				admin.Put("/acquisition/services/{code}/password", h.handleSetAcquisitionSecret("password"))
+				admin.Delete("/acquisition/services/{code}/password", h.handleSetAcquisitionSecret("password"))
 				admin.Get("/lidarr/quality-profiles", h.handleListQualityProfiles)
 				admin.Get("/lidarr/metadata-profiles", h.handleListMetadataProfiles)
 				admin.Get("/lidarr/root-folders", h.handleListRootFolders)
@@ -372,6 +383,8 @@ type handlers struct {
 	// acoustIDLookup is the AcoustID lookup worker (M401): its settings, its
 	// status and "look up now". Nil serves the defaults (off).
 	acoustIDLookup *library.AcoustIDLookupWorker
+	// acquisition is the operator's indexers and download clients (M502).
+	acquisition *acquire.Store
 	// leveled renders the leveled streams handed to Sonos/UPnP speakers
 	// (M464 #5001). Nil when its cache directory cannot be made: a level
 	// request then gets the plain stream.