feat: shorten DID in public note URLs by stripping did:plc: prefix

URLs are now /pub/<base32id>/rkey instead of /pub/did:plc:<base32id>/rkey.
Non-plc DIDs keep their method prefix (e.g. web:example.com).

src/modules/atproto/shortDid.ts

@@ -0,0 +1,6 @@
+export const toShortDid = (did: string) => did.replace(/^did:(plc:)?/, "")
+// did:plc:xxx → xxx, did:web:x → web:x
+
+export const fromShortDid = (shortDid: string) =>
+  shortDid.includes(":") ? `did:${shortDid}` : `did:plc:${shortDid}`
+// xxx → did:plc:xxx, web:x → did:web:x