Initial implementation of youtube-automate

A DVR for YouTube subscriptions, laid out so Jellyfin presents each channel
as a show and each video as an episode. Cron-driven, idempotent, with a
public admin UI for a non-operator.

Verified end to end on susan against three real channels: PO tokens, h264
downloads, Jellyfin resolution from local NFOs with all providers disabled,
retention and tombstones.

Corrections to the original design handover (specs.md documents each with
the evidence, and specs.handover-original.md preserves the original):

- The format sort selected 360p. Ranking acodec above res makes `bv*` prefer
  the combined 360p stream, which carries AAC, over the 720p video-only
  stream whose acodec is none. vcodec now leads, so a video without h264 at
  720p yields h264 lower down rather than VP9 this hardware cannot transcode.
- yt-dlp now requires a JS runtime and the yt-dlp-ejs solver scripts, which
  only ship with the [default] extra. Without them the n challenge fails and
  the mweb formats disappear entirely.
- --flat-playlist carries no upload dates, so the specced client-side date
  filter for backfill was impossible. Backfill is RSS-first.
- skipped_old was terminal, so raising a channel's retention appeared to do
  nothing. Added an explicit rescan.
- is_upcoming premieres now defer and retry instead of being skipped forever.
- TubeArchivist is gone, so the media root and the tube.jihakuz.xyz vhost
  were both reclaimed; the latter still pointed at its dead port.

240 offline tests, no network and no real yt-dlp invocation.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/test_settings.py

@@ -0,0 +1,110 @@
+"""Typed settings accessors and form validation."""
+
+import pytest
+
+from youtube_automate import settings as settings_module
+from youtube_automate.settings import DEFAULTS, Settings, validate, validate_all
+
+
+class TestAccessors:
+    def test_missing_key_returns_the_default(self, settings):
+        assert settings.get_int("retention_days") == 14
+        assert settings.get_str("sub_langs") == "en.*"
+        assert settings.get_bool("write_subs") is True
+
+    def test_unknown_key_never_raises(self, settings):
+        assert settings.get_str("no_such_key") == ""
+        assert settings.get_int("no_such_key") == 0
+
+    def test_set_then_get(self, settings):
+        settings.set("retention_days", "30")
+        assert settings.get_int("retention_days") == 30
+
+    def test_set_overwrites(self, settings):
+        settings.set("retention_days", "30")
+        settings.set("retention_days", "45")
+        assert settings.get_int("retention_days") == 45
+
+    def test_corrupt_integer_falls_back_to_the_default(self, settings):
+        settings.set("retention_days", "not a number")
+        assert settings.get_int("retention_days") == 14
+
+    @pytest.mark.parametrize("truthy", ["true", "True", "1", "yes", "on"])
+    def test_bool_truthy_forms(self, settings, truthy):
+        settings.set("write_subs", truthy)
+        assert settings.get_bool("write_subs") is True
+
+    @pytest.mark.parametrize("falsy", ["false", "False", "0", "no", "off", ""])
+    def test_bool_falsy_forms(self, settings, falsy):
+        settings.set("write_subs", falsy)
+        assert settings.get_bool("write_subs") is False
+
+    def test_corrupt_bool_falls_back_to_the_default(self, settings):
+        settings.set("write_subs", "maybe")
+        assert settings.get_bool("write_subs") is True
+
+    def test_all_editable_covers_every_default(self, settings):
+        values = settings.all_editable()
+        assert set(values) == set(DEFAULTS)
+
+    def test_secrets_are_not_editable(self):
+        for key in settings_module.SECRET_KEYS:
+            assert key not in settings_module.EDITABLE
+
+
+class TestValidation:
+    @pytest.mark.parametrize(
+        "key, value",
+        [
+            ("retention_days", "14"),
+            ("backfill_days", "0"),
+            ("max_height", "720"),
+            ("min_duration_seconds", "120"),
+            ("disk_cap_gb", "0"),
+            ("write_subs", "true"),
+            ("sponsorblock_mark", "false"),
+            ("jellyfin_url", "http://127.0.0.1:8096"),
+            ("pot_provider_url", "https://example.com:4416"),
+            ("sub_langs", "en.*"),
+        ],
+    )
+    def test_accepts_good_values(self, key, value):
+        ok, _ = validate(key, value)
+        assert ok
+
+    @pytest.mark.parametrize(
+        "key, value",
+        [
+            ("retention_days", "abc"),
+            ("retention_days", "0"),
+            ("retention_days", "-5"),
+            ("max_height", "10"),
+            ("min_duration_seconds", "-1"),
+            ("write_subs", "maybe"),
+            ("jellyfin_url", "not-a-url"),
+            ("jellyfin_url", "ftp://host/"),
+            ("jellyfin_url", "http://"),
+            ("sub_langs", ""),
+        ],
+    )
+    def test_rejects_bad_values(self, key, value):
+        ok, message = validate(key, value)
+        assert not ok
+        assert message
+
+    def test_validate_all_reports_each_bad_field(self):
+        errors = validate_all(
+            {"retention_days": "abc", "max_height": "720", "jellyfin_url": "nope"}
+        )
+        assert set(errors) == {"retention_days", "jellyfin_url"}
+
+    def test_validate_all_ignores_unknown_keys(self):
+        assert validate_all({"not_a_setting": "x"}) == {}
+
+    def test_empty_api_key_is_acceptable(self):
+        ok, _ = validate("jellyfin_api_key", "")
+        assert ok
+
+    def test_whitespace_is_tolerated(self):
+        ok, _ = validate("retention_days", "  21  ")
+        assert ok