Add NzbDAV as an alternative Usenet provider

[Jauntiness]

Add NzbDAV as an alternative Usenet provider

Summary

Adds NzbDAV as a second supported
usenet backend alongside the existing Decypharr integration. Both can be
selected at runtime via a config key / settings UI dropdown.

Why

The current DecypharrClient is tightly coupled to Decypharr's custom
endpoints (POST /api/add, GET /api/browse/nzbs/…, DELETE /api/torrents).
NzbDAV exposes a different (standard SABnzbd-style) API
(GET /api?mode=addfile, ?mode=queue, ?mode=history, …) and serves files
via WebDAV. Without a second client it cannot be wired into cli-debrid.

NzbDAV is a useful alternative because:

• It has a built-in HealthCheckService (automatic NZB-availability repair)
• It serves a WebDAV mount instead of FUSE-only, easier rclone-mounting

What's changed

New files

File	What
app/usenet/nzbdav_client.py	NzbdavClient — mirrors DecypharrClient's public interface 1:1
app/usenet/__init__.py	get_usenet_client() factory + provider-key reader

Modified files (minimal diffs)

File	Lines changed	What
app/usenet/decypharr_client.py	last ~14 lines (factory funcs only)	get_decypharr_client() delegates to NzbdavClient when provider == 'nzbdav'; class body untouched
app/routes/program_operation_routes.py	one block in check_service_connectivity()	hardcoded /version URL fetch replaced with client.check_connectivity() so it works for any provider
app/templates/settings_tabs/required_tangerine.html	banner text + Provider select + Mount Path field + 12-line inline JS	Provider dropdown, conditional field visibility (decypharr-only vs nzbdav-only fields shown based on selection)
app/static/js/scraper.js	3 strings	Submit-dialog text now provider-agnostic ("Submit to the Usenet provider" instead of "to Decypharr")
app/templates/debrid_manager.html	9 strings	Button titles + bulk-action dialogs now provider-agnostic

Backwards compatibility

• Existing installs without a provider key in Usenet Provider config
  default to decypharr → zero behaviour change.
• All 11 existing from usenet.decypharr_client import get_decypharr_client
  call sites keep working — the function is just provider-aware now.
• The DecypharrClient class itself is untouched.

Configuration

Settings → Required → Usenet Provider:

Field	Decypharr	NzbDAV
Provider	Decypharr (default)	NzbDAV
Provider URL	http://x:8888	http://x:3000
API Token	optional bearer	nzbdav api.key
Download Folder	category	category (must exist in nzbdav api.categories config)
Decypharr Data Path	required for backup tools	ignored
Mount Path	ignored	path where nzbdav-rclone-mount appears (used for browse helpers)

Provider-specific differences (documented in nzbdav_client.py)

DecypharrClient	NzbdavClient
POST /api/add with arr + downloadFolder form fields	POST /api?mode=addfile with cat query param
URL-add via server-side fetch + pre-fetch fallback for blocked indexers	mode=addurl with the same pre-fetch fallback
GET /api/browse/nzbs/<name> folder lookup	filesystem listdir under mounted_file_location (nzbdav has no browse API)
/api/repair/health/<n>/check trigger	no-op — nzbdav has internal HealthCheckService
DELETE /api/torrents?hashes=<uuid>	DELETE /api?mode=history&name=delete&value=<nzo_id>

Testing

Tested locally against:

• nzbdav v0.6.4 with rclone-sidecar
• cli-debrid :dev image
• Existing Decypharr install on the same box (provider-switch toggles cleanly)

Connectivity check confirms with provider-aware label:

INFO - Usenet provider (NzbDAV (Usenet)) reachable at http://192.168.1.x:3000
DEBUG - [Connectivity Check Task] Service connectivity check passed

Follow-ups (not in this PR)

• Add the same provider-dropdown to onboarding_step_2.html (initial setup
  wizard still hardcodes "Decypharr" wording)
• Update connections.html provider label display via PROVIDER_NAME
• Optional: migrate remaining 11 callers from get_decypharr_client() to
  get_usenet_client() for cleaner naming (purely cosmetic, no functional change)

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Closes / refs: (add issue link here)

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Follow-up commits in this PR

Title-based category routing (commit 98c3a98)

The original commit routes every grab to a single static SAB category
(download_folder, default cli_debrid). In a typical Plex setup that
folder is not a library location, so grabs stay invisible and cli_debrid
loops items between Wanted and Checking.

Added a title-based heuristic in nzbdav_client.py that derives the SAB
category from the release title before submission:

Title pattern	nzbdav category
Show + 1080p + (x264/h264/AVC)	shows_1080p_264
Show (else)	shows
Movie (year present) + 1080p + (x264/h264/AVC)	movies_1080p_264
Movie (else)	movies
Music markers (FLAC, MP3, hi-res, …)	music
Nothing detected	default_category (default __unplayable__)

Category names mirror zurg's filter-folder convention so the same Plex
library locations can feed from both providers. Centralized in a single
helper — covers all 11 add_nzb call sites including manual UI submits.

Backward-compatible: explicit category= arg still wins; unmatched titles
fall to default_category (= identical behavior to before, just renamed
from cli_debrid to __unplayable__).

Standalone docs (commit 2f669b7)

usenet/README.md — self-contained docs covering config, interface
differences vs DecypharrClient, the category-routing heuristic, and
optional companion setups (mergerfs union for direct file-detection,
Plex Smart Collections for quality views, separate _1080p Plex
libraries). Includes a "For LLMs / AI agents" section with code
anchors and smoke-test commands so the integration can be set up or
extended autonomously by AI assistants.

[Jauntiness]

Pushed 07a3089d, extending the NzbDAV support:

• In-app setup helper (templates/_nzbdav_setup_helper.html, in the Usenet Provider settings + onboarding step 2): client-side generator for the nzbdav docker-compose.yml + rclone.conf (+ an optional mergerfs union for multi-provider setups) + the cli-debrid config block, plus a live "test connection & ensure categories" tool backed by /api/nzbdav/{check,ensure_categories} in routes/program_operation_routes.py. These read/create the categories cli-debrid routes into via NzbDAV's get-config/update-config API — applied live, no restart (reachable without the SAB key when DISABLE_FRONTEND_AUTH=true).
• Host-side CLIs usenet/nzbdav_setup.py + nzbdav_migrate.py for what a container can't do from the GUI: migrate-files replays an existing Decypharr .nzb store into NzbDAV, plus headless wizard/generate, and a read-only preflight doctor (reachability, missing categories with --fix, mount visibility). stdlib-only.
• Repair/health re-wire so it works on NzbDAV (broken items from mode=history status=Failed, scoped to owned categories so it never touches another SAB client's entries; NzbDAV history-delete fixed to GET — DELETE was a silent no-op).
• Storage-agnostic subtitles: sidecar where the media dir is writable, otherwise Plex-API upload keyed on ratingKey (works on read-only WebDAV/rclone mounts).
• Settings clarity: relabeled the Usenet "Download Folder" field to "Fallback Category (rarely used)" and documented Plex.mounted_file_location for multi-provider / union setups.

Details in the commit message — feedback on the direction welcome.