fix: reliable YouTube tagging, loud Lidarr failures, deno runtime, repair recovery

Root cause of bad album/title tags: yt-dlp's --parse-metadata reads a
single-word FROM (matching field_to_template's ^[a-zA-Z_]+$) as a *field
name*, so literal one-word titles/albums like "Cochise" became "NA". Inject
literals via seed-then-replace into meta_<tag> instead (--parse-metadata to
create the field, --replace-in-metadata with literal args to set it), which
is immune to template parsing and also creates tags the source lacks.

- yt_download: literal-safe meta_artist/title/album; hit album no longer
  clobbered by the Unknown-Album default; artist tag now created when missing.
- lidarr_search: connection/timeout errors surface via err() ("Lidarr
  unreachable … falling back to YouTube") instead of silent dbg(), so the
  YouTube fallback isn't mistaken for "no Lidarr match".
- Dockerfile: install deno (arch-aware) — the JS runtime yt-dlp needs for
  YouTube; without it: "No supported JavaScript runtime" / HTTP 403.
- repair: treat NA/Unknown placeholders as bogus and overwrite title/artist
  from source (was fill-missing-only); normalise literal "NA" album to
  "Unknown Album"; rename bogus "NA [<id>]" filenames to the recovered title.
- README updated; .gitignore excludes server/log.txt.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/Dockerfile

@@ -1,7 +1,20 @@
 FROM python:3.12-slim
 
+# ffmpeg for audio extraction/embedding; deno is the JS runtime yt-dlp needs
+# for YouTube (without it: "No supported JavaScript runtime" -> missing formats
+# / HTTP 403). yt-dlp auto-detects deno on PATH.
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends ffmpeg \
+    && apt-get install -y --no-install-recommends ffmpeg ca-certificates curl unzip \
+    && arch="$(uname -m)" \
+    && case "$arch" in \
+         x86_64)  deno_arch=x86_64-unknown-linux-gnu ;; \
+         aarch64) deno_arch=aarch64-unknown-linux-gnu ;; \
+         *) echo "unsupported arch: $arch" >&2; exit 1 ;; \
+       esac \
+    && curl -fsSL "https://github.com/denoland/deno/releases/latest/download/deno-${deno_arch}.zip" -o /tmp/deno.zip \
+    && unzip /tmp/deno.zip -d /usr/local/bin \
+    && rm /tmp/deno.zip \
+    && apt-get purge -y --auto-remove curl unzip \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app