feat(releases): Phase 1 — new filesystem release domain + TmdbId VO

First step of specs/dot_alfred_v2.md. Introduces a separate bounded
context (alfred/domain/releases/) for the filesystem-side aggregates,
disjoint from TMDB identity which stays in tv_shows/ and movies/.
The link between the two worlds is TmdbId, used as the natural key
in the persistence layer (no domain-level reference).

New package alfred/domain/releases/:
- value_objects: EpisodeRange (covers SxxE01E02E03 multi-episode
  files via start/end inclusive range, with count/numbers/is_single
  helpers), ReleaseMode enum (PACK = N video files direct in the
  season folder, EPISODIC = N sub-folders).
- entities: TrackProfile, EpisodeRelease, SeasonRelease (with
  episode_count() summing each EpisodeRange.count()), SeriesRelease
  (tmdb_id primary anchor, optional imdb_id secondary), MovieRelease.
  All frozen dataclasses.
- builders: SeasonReleaseBuilder + SeriesReleaseBuilder mirroring
  the v1 TVShowBuilder pattern. Builders sort episodes by range
  start on emit and reject overlapping ranges (two files claiming
  the same TMDB slot). from_existing() seeds a builder from an
  existing frozen aggregate for round-trip edits.
- repositories: abstract ports (SeriesReleaseRepository,
  MovieReleaseRepository); concrete .alfred sidecar impls arrive
  in Phase 2.

New shared VO alfred/domain/shared/value_objects.py::TmdbId — positive
int, rejects bool/str/float, symmetric with the existing ImdbId VO.

73 unit tests cover VO validation, entity invariants, builder sort
+ overlap detection, and from_existing() round-trips.

v1 code paths are untouched at this stage; the new domain coexists
with the old TVShow aggregate until Phase 3 refactors it.

tests/domain/releases/test_value_objects.py

@@ -0,0 +1,106 @@
+"""Tests for the releases domain value objects: EpisodeRange, ReleaseMode."""
+
+import pytest
+
+from alfred.domain.releases.value_objects import EpisodeRange, ReleaseMode
+from alfred.domain.shared.exceptions import ValidationError
+from alfred.domain.tv_shows.value_objects import EpisodeNumber
+
+
+# ---------------------------------------------------------------------------
+# ReleaseMode
+# ---------------------------------------------------------------------------
+
+
+class TestReleaseMode:
+    def test_values(self):
+        assert ReleaseMode.PACK.value == "pack"
+        assert ReleaseMode.EPISODIC.value == "episodic"
+
+    def test_str_subclass(self):
+        # ReleaseMode is a (str, Enum) — string equality should work.
+        assert ReleaseMode.PACK == "pack"
+        assert ReleaseMode.EPISODIC == "episodic"
+
+
+# ---------------------------------------------------------------------------
+# EpisodeRange
+# ---------------------------------------------------------------------------
+
+
+class TestEpisodeRangeConstruction:
+    def test_single_episode(self):
+        r = EpisodeRange(EpisodeNumber(1), EpisodeNumber(1))
+        assert r.start == EpisodeNumber(1)
+        assert r.end == EpisodeNumber(1)
+
+    def test_multi_episode(self):
+        r = EpisodeRange(EpisodeNumber(2), EpisodeNumber(4))
+        assert r.start == EpisodeNumber(2)
+        assert r.end == EpisodeNumber(4)
+
+    def test_end_before_start_raises(self):
+        with pytest.raises(ValidationError):
+            EpisodeRange(EpisodeNumber(5), EpisodeNumber(3))
+
+    def test_start_must_be_episode_number(self):
+        with pytest.raises(ValidationError):
+            EpisodeRange(1, EpisodeNumber(2))  # type: ignore[arg-type]
+
+    def test_end_must_be_episode_number(self):
+        with pytest.raises(ValidationError):
+            EpisodeRange(EpisodeNumber(1), 2)  # type: ignore[arg-type]
+
+
+class TestEpisodeRangeOperations:
+    def test_count_single(self):
+        assert EpisodeRange(EpisodeNumber(1), EpisodeNumber(1)).count() == 1
+
+    def test_count_multi(self):
+        assert EpisodeRange(EpisodeNumber(1), EpisodeNumber(3)).count() == 3
+
+    def test_count_large(self):
+        assert EpisodeRange(EpisodeNumber(1), EpisodeNumber(10)).count() == 10
+
+    def test_numbers_single(self):
+        r = EpisodeRange(EpisodeNumber(2), EpisodeNumber(2))
+        assert r.numbers() == (EpisodeNumber(2),)
+
+    def test_numbers_multi(self):
+        r = EpisodeRange(EpisodeNumber(2), EpisodeNumber(4))
+        assert r.numbers() == (
+            EpisodeNumber(2),
+            EpisodeNumber(3),
+            EpisodeNumber(4),
+        )
+
+    def test_is_single_true(self):
+        assert EpisodeRange(EpisodeNumber(1), EpisodeNumber(1)).is_single()
+
+    def test_is_single_false(self):
+        assert not EpisodeRange(EpisodeNumber(1), EpisodeNumber(2)).is_single()
+
+    def test_str_single(self):
+        assert str(EpisodeRange(EpisodeNumber(2), EpisodeNumber(2))) == "E02"
+
+    def test_str_multi(self):
+        assert str(EpisodeRange(EpisodeNumber(2), EpisodeNumber(4))) == "E02-E04"
+
+    def test_repr(self):
+        r = EpisodeRange(EpisodeNumber(1), EpisodeNumber(3))
+        assert repr(r) == "EpisodeRange(1, 3)"
+
+    def test_equality(self):
+        a = EpisodeRange(EpisodeNumber(1), EpisodeNumber(3))
+        b = EpisodeRange(EpisodeNumber(1), EpisodeNumber(3))
+        c = EpisodeRange(EpisodeNumber(1), EpisodeNumber(2))
+        assert a == b
+        assert a != c
+
+    def test_hashable(self):
+        ranges = {
+            EpisodeRange(EpisodeNumber(1), EpisodeNumber(1)),
+            EpisodeRange(EpisodeNumber(1), EpisodeNumber(1)),
+            EpisodeRange(EpisodeNumber(2), EpisodeNumber(3)),
+        }
+        assert len(ranges) == 2