Implement Melora: *arr media arrival webhook announcer for Matrix

Replace Bellhop scaffolding with full Melora implementation:
- FastAPI webhook endpoints for Radarr, Sonarr, and Lidarr
- matrix-nio integration with threaded room posting
- SQLite for thread root persistence and event deduplication
- Message formatting with plain text and HTML for each media type
- Shared secret authentication via X-Arr-Webhook-Secret header
- Updated dependencies, configuration, and documentation

https://claude.ai/code/session_01DuzWyMMXvLMB4VxEwJyV4X

app/formatters.py

@@ -0,0 +1,120 @@
+import markdown as md
+
+
+def _render_html(text: str) -> str:
+    return md.markdown(text, extensions=["extra"])
+
+
+def _strip_markdown(text: str) -> str:
+    return text.replace("**", "").replace("*", "").replace("> ", "")
+
+
+def format_radarr(payload: dict) -> tuple[str, str]:
+    movie = payload.get("movie", {})
+    title = movie.get("title", "Unknown")
+    year = movie.get("year", "")
+    is_upgrade = payload.get("isUpgrade", False)
+
+    quality = (
+        payload.get("movieFile", {})
+        .get("quality", {})
+        .get("quality", {})
+        .get("name", "Unknown")
+    )
+
+    if is_upgrade:
+        lines = [
+            f"\U0001f3ac **{title}** ({year})",
+            f"> \u2b06\ufe0f *Quality upgrade*",
+            f"> \U0001f39e\ufe0f Quality: {quality}",
+        ]
+    else:
+        lines = [
+            f"\U0001f3ac **{title}** ({year})",
+            f"> \u2705 *New addition*",
+            f"> \U0001f39e\ufe0f Quality: {quality}",
+        ]
+
+    body_md = "\n".join(lines)
+    plain = _strip_markdown(body_md)
+    html = _render_html(body_md)
+    return plain, html
+
+
+def format_sonarr(payload: dict) -> tuple[str, str]:
+    series = payload.get("series", {})
+    series_title = series.get("title", "Unknown")
+    is_upgrade = payload.get("isUpgrade", False)
+
+    episodes = payload.get("episodes", [{}])
+    ep = episodes[0] if episodes else {}
+    season = ep.get("seasonNumber", 0)
+    episode = ep.get("episodeNumber", 0)
+    ep_title = ep.get("title", "")
+
+    quality = (
+        payload.get("episodeFile", {})
+        .get("quality", {})
+        .get("quality", {})
+        .get("name", "Unknown")
+    )
+
+    header = f"\U0001f4fa **{series_title}** \u2014 S{season:02d}E{episode:02d}"
+    if ep_title:
+        header += f" \u2014 *{ep_title}*"
+
+    if is_upgrade:
+        lines = [
+            header,
+            f"> \u2b06\ufe0f *Quality upgrade*",
+            f"> \U0001f39e\ufe0f Quality: {quality}",
+        ]
+    else:
+        lines = [
+            header,
+            f"> \u2705 *New addition*",
+            f"> \U0001f39e\ufe0f Quality: {quality}",
+        ]
+
+    body_md = "\n".join(lines)
+    plain = _strip_markdown(body_md)
+    html = _render_html(body_md)
+    return plain, html
+
+
+def format_lidarr(payload: dict) -> tuple[str, str]:
+    artist = payload.get("artist", {})
+    artist_name = artist.get("name", "Unknown")
+    album = payload.get("album", {})
+    album_title = album.get("title", "")
+    is_upgrade = payload.get("isUpgrade", False)
+
+    track_files = payload.get("trackFiles", [{}])
+    tf = track_files[0] if track_files else {}
+    quality = (
+        tf.get("quality", {})
+        .get("quality", {})
+        .get("name", "Unknown")
+    )
+
+    header = f"\U0001f3b5 **{artist_name}**"
+    if album_title:
+        header += f" \u2014 *{album_title}*"
+
+    if is_upgrade:
+        lines = [
+            header,
+            f"> \u2b06\ufe0f *Quality upgrade*",
+            f"> \U0001f3b5 Format: {quality}",
+        ]
+    else:
+        lines = [
+            header,
+            f"> \u2705 *New addition*",
+            f"> \U0001f3b5 Format: {quality}",
+        ]
+
+    body_md = "\n".join(lines)
+    plain = _strip_markdown(body_md)
+    html = _render_html(body_md)
+    return plain, html