feat(api): series, season and episode endpoints (#81)

crates/arr-db/migrations/0006_episode_releases.sql

@@ -0,0 +1,11 @@
+-- The TV counterpart of movie_releases (0003). One release comes back for
+-- more than one episode — a season pack matches every episode in the season —
+-- so the release row stays unique by indexer and guid, and each match is a
+-- row here.
+CREATE TABLE episode_releases (
+    episode_id INTEGER NOT NULL REFERENCES episodes (id) ON DELETE CASCADE,
+    release_id INTEGER NOT NULL REFERENCES releases (id) ON DELETE CASCADE,
+    PRIMARY KEY (episode_id, release_id)
+) STRICT;
+
+CREATE INDEX episode_releases_release ON episode_releases (release_id);