refactor(orbit): switch share link to psysonic2- magic string format

Aligns orbit invites with the existing magic-string family (psysonic1- for
server invites, psysonic2- for library shares) by folding orbit into the
psysonic2- payload as a new k:'orbit' variant. The JSON body is
intentionally extendable so future layers (passwords, permissions,
invite expiry) can be added without a format migration.

- SharePayloadV1 split into EntitySharePayloadV1 + OrbitSharePayloadV1
- decodeSharePayloadFromText filters orbit out; orbit has its own decoder
- applySharePastePayload param narrowed to EntitySharePayloadV1
- buildOrbitShareLink / parseOrbitShareLink kept as thin wrappers
- slug parameter dropped (magic string is opaque, so the slug was
  cosmetic-only in the old URL form); slugifyOrbitName removed as dead code
- joinModalLinkPlaceholder updated in all 8 locales

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/utils/shareLink.ts

@@ -5,10 +5,17 @@ export const PSYSONIC_SHARE_PREFIX = 'psysonic2-';
 
 export type EntityShareKind = 'track' | 'album' | 'artist';
 
-export type SharePayloadV1 =
+/** Entity / queue shares — what {@link applySharePastePayload} dispatches on. */
+export type EntitySharePayloadV1 =
   | { srv: string; k: EntityShareKind; id: string }
   | { srv: string; k: 'queue'; ids: string[] };
 
+/** Orbit invite — session id + originating server. Decoded separately so that
+ *  entity-share consumers can't accidentally receive an orbit payload. */
+export type OrbitSharePayloadV1 = { srv: string; k: 'orbit'; sid: string };
+
+export type SharePayloadV1 = EntitySharePayloadV1 | OrbitSharePayloadV1;
+
 export function normalizeShareServerUrl(url: string): string {
   const t = url.trim();
   if (!t) return '';
@@ -38,24 +45,38 @@ function isEntityKind(k: unknown): k is EntityShareKind {
 
 export function encodeSharePayload(payload: SharePayloadV1): string {
   const srvNorm = normalizeShareServerUrl(payload.srv);
-  const body =
-    payload.k === 'queue'
-      ? JSON.stringify({
-          v: 1,
-          srv: srvNorm,
-          k: 'queue',
-          ids: payload.ids.map(id => String(id).trim()).filter(Boolean),
-        })
-      : JSON.stringify({
-          v: 1,
-          srv: srvNorm,
-          k: payload.k,
-          id: String(payload.id).trim(),
-        });
+  let body: string;
+  if (payload.k === 'queue') {
+    body = JSON.stringify({
+      v: 1,
+      srv: srvNorm,
+      k: 'queue',
+      ids: payload.ids.map(id => String(id).trim()).filter(Boolean),
+    });
+  } else if (payload.k === 'orbit') {
+    body = JSON.stringify({
+      v: 1,
+      srv: srvNorm,
+      k: 'orbit',
+      sid: String(payload.sid).trim(),
+    });
+  } else {
+    body = JSON.stringify({
+      v: 1,
+      srv: srvNorm,
+      k: payload.k,
+      id: String(payload.id).trim(),
+    });
+  }
   return PSYSONIC_SHARE_PREFIX + utf8ToBase64Url(body);
 }
 
-export function decodeSharePayloadFromText(text: string): SharePayloadV1 | null {
+/**
+ * Decode an entity / queue share from pasted text. Returns null for orbit
+ * payloads (use {@link decodeOrbitSharePayloadFromText}) — so entity-share
+ * consumers can't be fed an orbit invite by accident.
+ */
+export function decodeSharePayloadFromText(text: string): EntitySharePayloadV1 | null {
   const idx = text.indexOf(PSYSONIC_SHARE_PREFIX);
   if (idx < 0) return null;
   const after = text.slice(idx + PSYSONIC_SHARE_PREFIX.length);
@@ -67,6 +88,7 @@ export function decodeSharePayloadFromText(text: string): SharePayloadV1 | null
     const srv = typeof raw.srv === 'string' ? normalizeShareServerUrl(raw.srv) : '';
     if (!srv) return null;
     const k = raw.k;
+    if (k === 'orbit') return null;
     if (k === 'queue') {
       const idsRaw = raw.ids;
       if (!Array.isArray(idsRaw) || idsRaw.length === 0) return null;
@@ -87,3 +109,24 @@ export function findServerIdForShareUrl(servers: ServerProfile[], shareSrv: stri
   const hit = servers.find(s => normalizeShareServerUrl(s.url) === norm);
   return hit?.id ?? null;
 }
+
+/** Decode an orbit invite from pasted text. Returns null for entity / queue shares. */
+export function decodeOrbitSharePayloadFromText(text: string): OrbitSharePayloadV1 | null {
+  const idx = text.indexOf(PSYSONIC_SHARE_PREFIX);
+  if (idx < 0) return null;
+  const after = text.slice(idx + PSYSONIC_SHARE_PREFIX.length);
+  const token = after.match(/^([A-Za-z0-9_-]+)/)?.[1];
+  if (!token) return null;
+  try {
+    const raw = JSON.parse(base64UrlToUtf8(token)) as Record<string, unknown>;
+    if (raw.v !== 1) return null;
+    if (raw.k !== 'orbit') return null;
+    const srv = typeof raw.srv === 'string' ? normalizeShareServerUrl(raw.srv) : '';
+    if (!srv) return null;
+    const sid = typeof raw.sid === 'string' ? raw.sid.trim().toLowerCase() : '';
+    if (!/^[0-9a-f]{8}$/.test(sid)) return null;
+    return { srv, k: 'orbit', sid };
+  } catch {
+    return null;
+  }
+}