feat(songs): LRC file upload and footer link

For songs with an `lrc` field in frontmatter:
- Verifies the file exists and is valid UTF-8 (warns and skips otherwise)
- Uploads to wiki as `File:<title>.lrc` via MediaWiki file API
- Idempotent: skips upload if SHA1 matches existing wiki file
- Appends `[[Media:<title>.lrc|Synced lyrics (.lrc)]]` before the
  category tag at the bottom of the wiki page

Songs without `lrc` in frontmatter are unaffected.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pipelines/songs/publish.py

@@ -1,7 +1,9 @@
 #!/usr/bin/env python3
-"""Songs pipeline renderer — converts source .md files to MediaWiki pages."""
+"""Songs pipeline — validates, renders, and publishes song .md files to MediaWiki."""
 
 import argparse
+import hashlib
+import io
 import os
 import subprocess
 import sys
@@ -57,10 +59,11 @@ def markdown_to_wikitext(body: str) -> str:
     return result.stdout
 
 
-def build_wikitext(fm: dict, body_wikitext: str, source_url: str, source_ref: str) -> str:
+def build_wikitext(fm: dict, body_wikitext: str, source_url: str, source_ref: str, lrc_filename: str | None = None) -> str:
     banner = f"{{{{Auto-generated|source={source_url}|commit={source_ref}}}}}"
     category = f"[[Category:{fm['album']}]]"
-    return f"{banner}\n\n{body_wikitext}\n{category}\n"
+    lrc_line = f"[[Media:{lrc_filename}|Synced lyrics (.lrc)]]\n" if lrc_filename else ""
+    return f"{banner}\n\n{body_wikitext}{lrc_line}{category}\n"
 
 
 def connect_wiki() -> mwclient.Site:
@@ -76,17 +79,57 @@ def connect_wiki() -> mwclient.Site:
     return site
 
 
+def upload_lrc(lrc_path: Path, title: str, site: mwclient.Site) -> bool:
+    """Upload LRC file to wiki if content has changed. Returns True if uploaded."""
+    if not lrc_path.exists():
+        print(f"  warn: LRC file not found: {lrc_path}", file=sys.stderr)
+        return False
+
+    content = lrc_path.read_bytes()
+    try:
+        content.decode("utf-8")
+    except UnicodeDecodeError:
+        print(f"  warn: {lrc_path} is not valid UTF-8 text, skipping LRC upload", file=sys.stderr)
+        return False
+
+    wiki_filename = f"{title}.lrc"
+    local_sha1 = hashlib.sha1(content).hexdigest()
+
+    if site.images[wiki_filename].imageinfo.get("sha1") == local_sha1:
+        return False
+
+    site.upload(
+        file=io.BytesIO(content),
+        filename=wiki_filename,
+        description=f"Synced lyrics for [[{title}]] (auto-published)",
+        ignore=True,
+    )
+    return True
+
+
 AUTO_BANNER_PREFIX = "{{Auto-generated"
 
 
-def publish_one(rel: Path, post, site: mwclient.Site, source_ref: str, gitea_repo_url: str) -> str:
+def publish_one(abs_path: Path, source_dir: Path, post, site: mwclient.Site, source_ref: str, gitea_repo_url: str) -> str:
     """Returns 'published', 'noop', or 'skipped-manual'."""
+    rel = abs_path.relative_to(source_dir)
     fm = post.metadata
+    title = str(fm["title"])
+
     body_wikitext = markdown_to_wikitext(strip_first_h1(post.content))
     source_url = f"{gitea_repo_url}/src/commit/{source_ref}/{rel}"
-    page_content = build_wikitext(fm, body_wikitext, source_url, source_ref)
 
-    page = site.pages[fm["title"]]
+    lrc_filename = None
+    lrc_rel = fm.get("lrc")
+    if lrc_rel:
+        lrc_uploaded = upload_lrc(abs_path.parent / str(lrc_rel), title, site)
+        lrc_filename = f"{title}.lrc"
+        if lrc_uploaded:
+            print(f"  [lrc-uploaded] {lrc_filename}")
+
+    page_content = build_wikitext(fm, body_wikitext, source_url, source_ref, lrc_filename)
+
+    page = site.pages[title]
     existing = page.text()
 
     if existing and not existing.startswith(AUTO_BANNER_PREFIX):
@@ -168,7 +211,7 @@ def main() -> None:
     counts = {"published": 0, "noop": 0, "skipped-manual": 0}
     for abs_path, post in posts.items():
         rel = abs_path.relative_to(source_dir)
-        outcome = publish_one(rel, post, site, source_ref, gitea_repo_url)
+        outcome = publish_one(abs_path, source_dir, post, site, source_ref, gitea_repo_url)
         counts[outcome] += 1
         if outcome == "skipped-manual":
             print(f"  [skipped-manual] {rel}  ← page exists without auto-gen banner; delete or add banner to hand over to bot", file=sys.stderr)