Merge ditto/main into agora

Pulls in 387 commits from ditto/main while preserving Agora-specific
features. Where the two codebases diverged on the same concept, kept
the Agora side per project direction.

Kept Agora-specific:
- SparkWallet stack (over Ditto's nostr-derived Bitcoin wallet)
- Communities (NIP-72 + chat + members), Messages, Organizers,
  Actions, Verified, Appearance settings
- DMProviderWrapper, country/organizer moderation in NoteMoreMenu
- 'Agora' branding, pub.agora.app bundle ID, version 2.8.0
- Built-in theme system (src/themes.ts) only

Rejected from Ditto:
- All Blobbi virtual pet code (80+ files, route, provider, sidebar,
  kind labels, feed setting, NIP.md entries, CSS animations)
- Custom theme events (kinds 36767/16767) — ThemesPage, ThemeContent,
  active profile themes, theme snapshot recovery
- On-chain zaps (kind 8333) and the entire Bitcoin wallet implementation
  (useBitcoinWallet, bitcoin-signers, BitcoinContentHeader,
  bitcoinjs-lib / @bitcoinerlab/secp256k1 / ecpair / tiny-secp256k1)
- ZapSuccessScreen (depended on dropped bitcoin lib)

Pulled in from Ditto:
- .agents/skills/* (12 new specialized skills, slim AGENTS.md)
- @nostrify bumps to 0.52 / 0.6 / 0.37
- New routes/pages: Music, Podcasts, Videos, Vines, Wikipedia, Books,
  Bluesky, Archive, AIChat, Trends, Webxdc, Highlights, Decks, Emojis,
  Development, Treasures, Colors, Packs
- Birdstar feed integration (kinds 2473, 12473, 30621)
- Wikipedia/Wikidata/Scryfall lookup in ExternalContentPage
- release-notes CI job + extract-release-notes.mjs script
- nsite:// URI handling in feed/sidebar
- iOS fastlane setup
- src/lib/avatarShape.ts + Avatar shape prop (kept for new Music/People
  components that depend on it)

Preserved Agora's ABSOLUTE 'NEVER COMMIT' rule at the top of AGENTS.md
and dropped Ditto's contradicting 'Commit at the end of every task'
section.

Validation: npm run test passes (tsc, eslint, 40/40 vitest, vite build).

CONTRIBUTING.md

@@ -44,6 +44,8 @@ Read the full "Understanding Agora" section above for the complete vision.
 
 One bug, one merge request. Fix exactly one thing. Don't bundle unrelated changes, don't sneak in refactors, don't "clean up while you're in there." Small, focused MRs get reviewed fast. Large ones sit.
 
+When the bug was introduced by an identifiable prior commit, add a `Regression-of: <short-sha>` trailer to the bottom of your commit message. See AGENTS.md "Attributing Regressions" for the convention.
+
 ### New features and significant changes
 
 Every feature MR must link to an existing open issue and clearly align with the "Understanding Agora" section in this file. The philosophy alignment section in the MR template is where you make the case for why your change belongs in Agora. If you can't articulate that clearly, the change probably doesn't belong.
@@ -131,6 +133,7 @@ maintain it long-term. For each finding, state the file, line, and issue.
 - [ ] Are there any new images >100KB or other large binary assets that should be hosted externally?
 - [ ] Is there any use of dangerouslySetInnerHTML, eval, innerHTML, or SVG string interpolation?
 - [ ] Is any data from a Nostr event (tags, content, pubkey, URLs) used in a security-sensitive context (href, src, query filter, trust decision) without validation?
+- [ ] If this is a bug fix and the offending commit is identifiable, does the commit message include a `Regression-of: <short-sha>` trailer? (See AGENTS.md "Attributing Regressions".)
 
 Skip anything a linter or type checker would catch. Focus on logic, data flow, and intent.