Keep the feed catalogue and server settings in the database

Phase 3 of #18. Two tables: catalogue (each feed's config::Feed as JSON, so a
new feed setting needs no column) and settings (general: the five server
settings the admin page edits). config.toml keeps what is needed before the
database is reached, or decides who gets in: paths, [torrent], [web].

ipx still runs from one in-memory Config, assembled at start from both
(assemble_config). The eight places that saved config.toml and re-read it now
call Ctx::store_cfg, which writes the database and swaps the copy in memory; the
first-run web token, which is config.toml's, is written there.

The first start on a database with no catalogue imports config.toml's feeds and
settings in one transaction whose first insert is the settings row, so two ipx
starting at once cannot both import; it then trims config.toml, keeping the
original as config.toml.pre-database. After that, feeds written into the file are
ignored with a warning. copy-db skips it, and copies both tables.

Rehearsed on a clone of production's database with production's config: all 130
feeds imported, the file trimmed, and the feed list, settings and directory
identical to the live server's.

Postgres connections now ask for no notices. Every CREATE ... IF NOT EXISTS on an
existing table sends one, eleven per open; sqlx logs them, and
tracing-subscriber 0.3.23's per-layer filters then dropped the next line ipx
logged -- the import's own message went missing that way. Proved by toggling it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/configuration.md

@@ -1,7 +1,19 @@
 # Configuration
 
-One TOML file, read at startup and re-read whenever the web UI writes to it — most changes take
-effect without a restart. Default location `$XDG_CONFIG_HOME/ipx/config.toml`
+Two places. **config.toml** holds what ipx needs before it reaches its database, and what decides
+who gets in: where things are (`download_dir`, `socket`, `organize`), `[torrent]` and `[web]`.
+**The database** holds the catalogue of feeds (`[feeds.<id>]` below) and the server settings the
+admin page edits (`schedule`, `max_total_gb`, `max_age_days`, `max_new_per_check`,
+`media_types`). Change those in the web UI, or with `ipx add`, `ipx rm` and `ipx import`; they
+take effect without a restart.
+
+The first time ipx meets a database that holds no catalogue, it takes the feeds and those
+settings from config.toml, then rewrites config.toml without them, keeping the original beside it
+as `config.toml.pre-database`. After that, feeds or those settings written into config.toml are
+ignored, with a warning in the log saying so. The sections below describe them as they were
+written in config.toml, which is still how a fresh install begins.
+
+config.toml's default location is `$XDG_CONFIG_HOME/ipx/config.toml`
 (`~/.config/ipx/config.toml`), overridden with `--config` or `$IPX_CONFIG`.
 
 | What | Where | Override |
@@ -30,6 +42,9 @@ max_new_per_check = 3               # per feed, per scan. 0 = unlimited
 media_types       = ["audio", "video"]
 ```
 
+`schedule`, `max_total_gb`, `max_age_days`, `max_new_per_check` and `media_types` move into the
+database as described above; `download_dir`, `socket` and `organize` stay in config.toml.
+
 * **`schedule`** — how often feeds are re-checked. A feed's own `<ttl>` still wins when it asks to
   be polled *less* often, and a per-feed `schedule` overrides both. Admin-only from the UI.
 * **`organize`** — `feed` files downloads under the feed's folder; `date` under `YYYY-MM-DD`.
@@ -90,8 +105,9 @@ itself carry a credential. Put TLS in front of it if that matters.
 
 ## `[feeds.<id>]`
 
-The table key is the feed id: stable, human-readable, and used in paths and the API. `ipx add`
-derives it from the feed title.
+Kept in the database once ipx has moved them in: a feed's settings are changed in the web UI, and
+feeds come and go with `ipx add`, `ipx rm` and `ipx import`. The table key is the feed id: stable,
+human-readable, and used in paths and the API. `ipx add` derives it from the feed title.
 
 ```toml
 [feeds.atp]
@@ -109,8 +125,8 @@ With more than one account, **`keywords`, `auto_download`, `allow_explicit` and
 config.toml are the fallback for a feed nobody has claimed. The keys above describe the feed itself
 and are the same for everyone. See [users.md](users.md).
 
-Feeds derived from a subscribed OPML are **not** written here: the OPML is the source of truth and
-they are re-derived on every scan. Editing one in the UI promotes it to a real config entry.
+Feeds derived from a subscribed OPML are **not** in the catalogue: the OPML is the source of truth
+and they are re-derived on every scan. Editing one in the UI promotes it to a catalogue entry.
 
 ## Environment