Initial commit: playlink music library hardlink deduplicator

Go backend (chi, SQLite) with an embedded React/TypeScript UI that finds
songs present in both a host and a slave music library and replaces the
slave copy with a hardlink to the host copy.

- Path-first matching with format/title/album-folder fallbacks
- Auto-linking of byte-identical files, re-verified with cmp before linking
- Manual review with ffprobe quality comparison, downgrade guard and
  promote-to-host override
- Build mode to populate an empty slave library from the host
- Dry run by default, atomic stage+rename replacement, quarantine with
  retention, undo, path confinement and authenticated UI
- Dockerfile and compose file for Unraid

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/api.ts

@@ -0,0 +1,160 @@
+export class ApiError extends Error {
+  constructor(public status: number, message: string) {
+    super(message);
+  }
+}
+
+async function request<T>(method: string, path: string, body?: unknown): Promise<T> {
+  const res = await fetch(`/api${path}`, {
+    method,
+    credentials: "same-origin",
+    headers: {
+      "X-Playlink-Request": "1",
+      ...(body !== undefined ? { "Content-Type": "application/json" } : {}),
+    },
+    body: body !== undefined ? JSON.stringify(body) : undefined,
+  });
+  const data = await res.json().catch(() => ({}));
+  if (!res.ok) throw new ApiError(res.status, data.error ?? res.statusText);
+  return data as T;
+}
+
+export const api = {
+  get: <T>(p: string) => request<T>("GET", p),
+  post: <T>(p: string, b: unknown = {}) => request<T>("POST", p, b),
+  put: <T>(p: string, b: unknown) => request<T>("PUT", p, b),
+  del: <T>(p: string) => request<T>("DELETE", p),
+};
+
+export type AuthState = { setup_required: boolean; authenticated: boolean; username?: string };
+
+export type Info = {
+  version: string;
+  allowed_roots: string[];
+  default_extensions: string[];
+  dry_run: boolean;
+};
+
+export type Job = {
+  id: number;
+  pair_id: number;
+  kind: string;
+  state: "running" | "done" | "failed" | "cancelled";
+  phase: string;
+  done: number;
+  total: number;
+  message: string;
+  error: string;
+  results: Record<string, number>;
+  skipped: string[];
+  started_at: number;
+  finished_at?: number;
+};
+
+export type Summary = {
+  counts: Record<string, number>;
+  review: number;
+  ignored: number;
+  reclaimable_bytes: number;
+  linked_bytes: number;
+};
+
+export type Pair = {
+  id: number;
+  name: string;
+  host_root: string;
+  slave_root: string;
+  quarantine_dir: string;
+  extensions: string[];
+  auto_link_identical: boolean;
+  scan_interval_minutes: number;
+  retention_days: number;
+  settle_minutes: number;
+  last_scan_at: number | null;
+  last_scan_error: string;
+  last_scan_warnings: string[];
+  summary: Summary;
+  job: Job | null;
+};
+
+export type PairInput = Pick<
+  Pair,
+  | "name"
+  | "host_root"
+  | "slave_root"
+  | "quarantine_dir"
+  | "extensions"
+  | "auto_link_identical"
+  | "scan_interval_minutes"
+  | "retention_days"
+  | "settle_minutes"
+>;
+
+export type ProbeInfo = {
+  codec: string;
+  codec_long?: string;
+  format?: string;
+  lossless: boolean;
+  bitrate: number;
+  sample_rate: number;
+  bit_depth?: number;
+  channels: number;
+  duration: number;
+  title?: string;
+  artist?: string;
+  album?: string;
+  error?: string;
+};
+
+export type Verdict = { better: "host" | "slave" | "equal" | "unknown"; duration_delta: number; notes: string[] | null };
+
+export type Status = "linked" | "identical" | "different" | "similar" | "unmatched" | "error";
+
+export type Match = {
+  id: number;
+  pair_id: number;
+  rel_slave: string;
+  rel_host: string;
+  kind: "path" | "path_case" | "extension" | "fuzzy" | "elsewhere" | "none";
+  status: Status;
+  host_size: number;
+  host_mtime: number;
+  slave_size: number;
+  slave_mtime: number;
+  host_probe?: ProbeInfo;
+  slave_probe?: ProbeInfo;
+  verdict?: Verdict;
+  note: string;
+  ignored: boolean;
+};
+
+export type Operation = {
+  id: number;
+  pair_id: number;
+  action: "link" | "promote" | "build" | "remove";
+  rel_host: string;
+  rel_slave: string;
+  rel_new: string;
+  quarantine_path: string;
+  quarantine_side: string;
+  bytes: number;
+  dry_run: boolean;
+  trigger: string;
+  status: "running" | "done" | "failed" | "planned" | "interrupted";
+  error: string;
+  created_at: number;
+  finished_at: number | null;
+  undone_at: number | null;
+  purged_at: number | null;
+};
+
+export type TreeEntry = {
+  name: string;
+  rel: string;
+  dir: boolean;
+  size?: number;
+  state?: "linked" | "conflict" | "missing";
+  linked?: number;
+};
+
+export type Page<T> = { items: T[]; total: number };