Add the Config view: edit and save the settings, applied without a restart

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

SPECS.md

@@ -69,7 +69,8 @@ Notes:
   Posters are JPEG/PNG, decoded and downscaled in the process. Library items fetch `/MediaCover/<id>/poster-250.jpg` from their Radarr/Sonarr instance with the API key; search results fall back to the provider's `remoteUrl` (fetched without credentials). Posters are cached in memory (the terminal's copies are deleted when the cache is dropped and on exit), failed downloads are not retried for two minutes, and the poster shrinks or disappears when the pane is too short. `ui.covers: false` disables it.
 - **Calendar view (F5):** a two-week window (starting today, moved a week at a time with `[`/`]`, `t` returns to today) with the library's movie releases and airing episodes, grouped by day. Radarr `GET /calendar` supplies the cinema, digital and physical release dates (taken as written: midnight UTC means that calendar day) and Sonarr `GET /calendar?includeSeries=true` the episodes with their air time (shown in local time). Unmonitored items are included with `u`. A movie appears once per release date in the window. Each entry shows type, title, episode or release kind and status (downloaded / missing / upcoming); the detail pane shows poster and plot; `Enter`/`i` starts the release search and `s` an automatic search.
 - **Download notifications:** a background poller (independent of the visible view) reads SABnzbd's history every 15 s and announces downloads that reach `Completed` or `Failed` as a popup and log entry; the first poll only records the current state. `ui.notify_downloads` (default true) and `ui.bell` (default false, rings the terminal bell) control it. Connection errors are not reported here, the indicators and the log already do that.
-- **Notifications and log (F5):** feedback about actions (added, deleted, grabbed, failures) appears as popups in the bottom right that fade away (errors stay longer). Everything is also kept in the Log view; only connection changes of the background polling are logged, not every failed poll.
+- **Config view (F7):** a form for every setting of the config file, in four sections (Radarr, Sonarr, SABnzbd, Interface) plus Test connections / Save / Revert. The fields start from the settings in use; API keys are masked (a checkbox shows them). `Test connections` builds temporary clients from the typed values and reports each service. `Save` validates like startup does (URLs, non-empty keys, refresh 1–3600 s), then writes the file from the file's own contents plus the edits (`config.LoadFile`), so values that only come from `ARR_TUI_*` environment variables are left as the file has them and are shown greyed out; the write is atomic (temp file + rename) and keeps the file's permissions (`0600` when new); defaults such as `covers: true` stay out of the file unless it already named them. Everything then applies without a restart: the Radarr/Sonarr/SABnzbd clients are re-pointed (`Reconfigure`, guarded by a mutex), the connection indicators, add-form defaults and options are refreshed, the library and calendar reload, the Downloads interval, notifications, bell and poster style are switched live. `q` and `?` are typed text in this view (`F9` opens the help).
+- **Notifications and log (F6):** feedback about actions (added, deleted, grabbed, failures) appears as popups in the bottom right that fade away (errors stay longer). Everything is also kept in the Log view; only connection changes of the background polling are logged, not every failed poll.
 
 ### 4.2 v0.2 (done, M8)
 
@@ -100,7 +101,7 @@ Layout sketch (Library view; the other views follow the same frame):
 └────────────────────────────────────────────────────────────────────┘
 ```
 
-Popups for action feedback appear in the bottom right and fade away; the Log view (F5) keeps the history.
+Popups for action feedback appear in the bottom right and fade away; the Log view (F6) keeps the history.
 
 tview primitives: `Pages` (views and stacked overlays), `Flex` (layout), `InputField` (search), `List`/`Table` (results, queues, library), `TextView` (details, log), `Form` (add dialog), `Modal` (confirmations). Popups are drawn by a wrapper around the root primitive.
 
@@ -108,7 +109,7 @@ Keybindings (the status bar shows the ones that apply to the current view):
 
 | Key | Action |
 |---|---|
-| `F1-F6` | Switch view (Movies, Series, Library, Downloads, Calendar, Log); also while typing, and from full-screen views. Dialogs block them. |
+| `F1-F7` | Switch view (Movies, Series, Library, Downloads, Calendar, Log, Config); also while typing, and from full-screen views. Dialogs block them. |
 | `Tab` / `Shift+Tab` | Switch panel within the current view (never the view): search box / results, Downloads panels, Library lists |
 | `?` / `F9` | Help (`F9` also works while typing) |
 | `q` / `Ctrl+C` | Quit |
@@ -204,7 +205,7 @@ The file should be created with mode `0600`; warn if it is more permissive. API
 - [x] **M6** — Interactive release search (movies, then series seasons/episodes) and grab.
 - [x] **M7** — Polish: help screen (`?`/F9), per-service connection indicators, README, Makefile release builds, `--version`.
 - [x] **M8** — Library view (movies/series, filters, text filter, monitor toggle, automatic search) and series drill-down (seasons/episodes, monitoring, search, release search).
-- [x] **M9** — Popup notifications, Log view (F5), context-sensitive key hints in the status bar.
+- [x] **M9** — Popup notifications, Log view (F6), context-sensitive key hints in the status bar.
 - [x] **M10** — Download completion notifications, remove from library, calendar view (F5; the Log moves to F6). Multiple instances per service are out of scope.
 - [ ] **M11+** — ideas: more library actions (edit quality profile, root folder), history of grabs per title.