docs: add block/mute user relations, emoji-sync CLI, and uid indexes

- Add `/block`, `/mute` endpoints with block/unblock and mute/unmute functionality in `routers/relations.py`, hiding blocked users' content everywhere except their own profile while muting only suppresses notifications
- Introduce `devplace emoji-sync` CLI command to regenerate `static/js/emoji-shortcodes.js` from the emoji library, documented in `CLAUDE.md` and wired in `cli.py`
- Create `get_blocked_uids()` database helper and apply it in `content.py` `load_detail()` to filter blocked users' posts from detail views
- Implement `_uid_index()` and `_drop_index()` helpers in `database.py` for unique uid indexes across tables, with `user_relations` added to `SOFT_DELETE_TABLES`
- Document new routes in `AGENTS.md` and `README.md`, including emoji shortcodes rendering behavior distinct from the emoji picker

tests/e2e/profile/search.py

@@ -522,7 +522,7 @@ def test_ui_media_lightbox_opens(alice):
     thumb.click()
     overlay = page.locator(".lightbox-overlay.visible")
     overlay.wait_for(state="visible")
-    assert page.locator(".lightbox-overlay.visible .lightbox-image").is_visible()
+    expect(page.locator(".lightbox-overlay.visible .lightbox-image")).to_be_visible()
     page.locator(".lightbox-overlay.visible .lightbox-close").click()
     overlay.wait_for(state="hidden")