feat(locks): add the Unlocked profile screen (#2005)

[Taewa]

Closes #2005. Part of #1998, stacked on #2003 — base is feat/2003-locks-reader-integration, review that first. Draft until #2252 merges.

What this adds

• A screen at /profile/unlocked listing the content the signed-in reader has unlocked, newest first.
• An Unlocked entry with a count in the profile sidebar and the mobile menu. Own profile only — the data lives in the reader's /priv, so another user's profile has none.
• Cards that render like the feed does: article titles, images, videos, file downloads, link embeds. Reuses the existing post renderers rather than adding lock-specific ones.

Behaviour worth knowing

• One read per profile visit. The profile layout survives tab navigation, so the sidebar count and the screen share a single read instead of enumerating /priv twice.
• Media loads per card, and is released when the card unmounts. Loading every attachment up front would pull the reader's whole unlocked library onto one screen.
• Interrupted replications never appear. A lock only counts once its completion marker is stored.
• A corrupt or missing entry drops on its own — the rest of the list still renders. A transient failure fails the whole read instead, so an outage doesn't look like lost content.
• Ordered by the homeserver's write time, not a timestamp the client writes into the file.
• Long posts expand in place. An unlocked copy has no post page to open, so "Show more" would otherwise do nothing. Existing feed cards are unaffected — they still navigate.

Not in scope

• collection posts
• Caching. Re-entering the profile re-reads the list; Locks: cache lock descriptors and unlocked posts in IndexedDB #2296 moves this to IndexedDB.

Notes for review

• No pagination — the list loads in full, matching the ticket.
• docs/locks.md has a new section covering the flow and the decisions above.

[Taewa]

https://github.com/pubky/pubky-homeserver/blob/1106eb02360b0bce88b0a6136f85f20308caebac/pubky-sdk/bindings/js/pkg/tests/events.ts#L110 <- This should be used instead of list() because this fn returns as chronological order / reversed.