Add per-repo cover image support for RSS feed items

Add image_url column to repos table with migration, CLI image add/remove
commands, and Media RSS <media:content> elements in generated feed output.

New CLI commands: ghrel image add <repo> <url>, ghrel image remove <repo>

tests/test_db.py

@@ -131,6 +131,81 @@ class TestGetAllEntries:
         assert len(entries) == 3
 
 
+class TestRepoImage:
+    def test_set_image(self, conn):
+        db.add_repo(conn, "owner/repo")
+        assert db.set_repo_image(conn, "owner/repo", "https://example.com/logo.png") is True
+        row = conn.execute("SELECT image_url FROM repos WHERE owner_repo = 'owner/repo'").fetchone()
+        assert row[0] == "https://example.com/logo.png"
+
+    def test_set_image_nonexistent(self, conn):
+        assert db.set_repo_image(conn, "no/one", "https://example.com/logo.png") is False
+
+    def test_set_image_overwrites(self, conn):
+        db.add_repo(conn, "owner/repo")
+        db.set_repo_image(conn, "owner/repo", "https://example.com/old.png")
+        db.set_repo_image(conn, "owner/repo", "https://example.com/new.png")
+        row = conn.execute("SELECT image_url FROM repos WHERE owner_repo = 'owner/repo'").fetchone()
+        assert row[0] == "https://example.com/new.png"
+
+    def test_remove_image(self, conn):
+        db.add_repo(conn, "owner/repo")
+        db.set_repo_image(conn, "owner/repo", "https://example.com/logo.png")
+        assert db.remove_repo_image(conn, "owner/repo") is True
+        row = conn.execute("SELECT image_url FROM repos WHERE owner_repo = 'owner/repo'").fetchone()
+        assert row[0] is None
+
+    def test_remove_image_no_image_set(self, conn):
+        db.add_repo(conn, "owner/repo")
+        assert db.remove_repo_image(conn, "owner/repo") is False
+
+    def test_image_url_in_entries(self, conn):
+        repo_id = db.add_repo(conn, "owner/repo")
+        db.set_repo_image(conn, "owner/repo", "https://example.com/logo.png")
+        db.upsert_entry(conn, repo_id, "release", "v1", "v1", "", "2025-01-01", "http://x")
+        entries = db.get_all_entries(conn)
+        assert len(entries) == 1
+        assert entries[0]["image_url"] == "https://example.com/logo.png"
+
+    def test_image_url_none_by_default(self, conn):
+        repo_id = db.add_repo(conn, "owner/repo")
+        db.upsert_entry(conn, repo_id, "release", "v1", "v1", "", "2025-01-01", "http://x")
+        entries = db.get_all_entries(conn)
+        assert entries[0]["image_url"] is None
+
+    def test_migration_adds_column(self):
+        """Test that _migrate_add_image_url adds the column if missing."""
+        c = sqlite3.connect(":memory:")
+        c.execute("PRAGMA foreign_keys=ON")
+        c.execute("""
+            CREATE TABLE repos (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                owner_repo TEXT NOT NULL UNIQUE,
+                mode TEXT NOT NULL DEFAULT 'release'
+            )
+        """)
+        c.execute("""
+            CREATE TABLE entries (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                repo_id INTEGER NOT NULL,
+                kind TEXT NOT NULL CHECK(kind IN ('release', 'tag')),
+                tag_name TEXT NOT NULL,
+                title TEXT NOT NULL,
+                body TEXT DEFAULT '',
+                published_at DATETIME NOT NULL,
+                html_url TEXT NOT NULL,
+                fetched_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+                FOREIGN KEY (repo_id) REFERENCES repos(id) ON DELETE CASCADE,
+                UNIQUE(repo_id, tag_name)
+            )
+        """)
+        c.commit()
+        db._migrate_add_image_url(c)
+        columns = [col[1] for col in c.execute("PRAGMA table_info(repos)").fetchall()]
+        assert "image_url" in columns
+        c.close()
+
+
 class TestGetConnection:
     def test_creates_file(self):
         with tempfile.TemporaryDirectory() as tmp: