Add Kagi-specific automated registration script and update README.

Changes:
- Move setup-kagi-aggregator.sh to kagi-news/scripts/setup.sh
- Add comprehensive Registration section to README
- Document automated vs manual setup options
- Explain registration workflow and requirements
- Update project structure to reflect new scripts

The setup script automates all 4 registration steps:
1. PDS account creation
2. .well-known file generation
3. Coves registration via XRPC
4. Service declaration creation

This makes the Kagi aggregator self-contained and ready to be
split into its own repository.

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Co-Authored-By: Claude <noreply@anthropic.com>

Add comprehensive setup scripts and documentation for aggregator registration.

Scripts:
- 1-create-pds-account.sh: Create PDS account for aggregator
- 2-setup-wellknown.sh: Generate .well-known/atproto-did file
- 3-register-with-coves.sh: Register with Coves instance via XRPC
- 4-create-service-declaration.sh: Create service declaration record

Documentation:
- Detailed README with step-by-step instructions
- Troubleshooting guide
- Configuration examples (nginx/Apache)
- Security best practices

These scripts automate the 4-step process of:
1. Creating a DID for the aggregator
2. Proving domain ownership
3. Registering with Coves
4. Publishing service metadata

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Co-Authored-By: Claude <noreply@anthropic.com>

Implement social.coves.aggregator.register endpoint for aggregator registration.

Features:
- Lexicon schema for registration request/response
- Domain verification via .well-known/atproto-did
- DID resolution and validation
- User table insertion for aggregators
- Comprehensive integration tests

The endpoint allows aggregators to register with a Coves instance by:
1. Providing their DID and domain
2. Verifying domain ownership via .well-known file
3. Getting indexed into the users table

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Co-Authored-By: Claude <noreply@anthropic.com>

Implements mandatory bidirectional did:web verification matching Bluesky's
security model. This prevents domain impersonation attacks by requiring
DID documents to claim the handle domain in their alsoKnownAs field.

Security Improvements:
- MANDATORY bidirectional verification (hard-fail, not soft-fail)
- Verifies domain matching (handle domain == hostedBy domain)
- Fetches DID document from https://domain/.well-known/did.json
- Verifies DID document ID matches claimed DID
- NEW: Verifies DID document claims handle in alsoKnownAs field
- Rejects communities that fail verification (was: log warning only)
- Cache TTL increased from 1h to 24h (matches Bluesky recommendations)

Implementation:
- Location: internal/atproto/jetstream/community_consumer.go
- Verification runs in AppView Jetstream consumer (not creation API)
- Impact: Controls AppView indexing and federation trust
- Performance: Bounded LRU cache (1000 entries), rate limiting (10 req/s)

Attack Prevention:
✓ Domain impersonation (can't claim did:web:nintendo.com without owning it)
✓ DNS hijacking (bidirectional check fails even with DNS control)
✓ Reputation hijacking (can't point your domain to someone else's DID)
✓ AppView pollution (only legitimate communities indexed)
✓ Federation trust (other instances can verify instance identity)

Tests:
- Updated existing tests to handle mandatory verification
- Added comprehensive bidirectional verification tests with mock HTTP server
- All tests passing ✅

Documentation:
- PRD_BACKLOG.md: Marked did:web verification as COMPLETE
- PRD_ALPHA_GO_LIVE.md: Added production deployment requirements
- Clarified architecture: AppView (coves.social) + PDS (coves.me)
- Added PDS deployment checklist (separate domain required)
- Updated production environment checklist
- Added Jetstream configuration (Bluesky production firehose)

Production Requirements:
- Deploy .well-known/did.json to coves.social with alsoKnownAs field
- Set SKIP_DID_WEB_VERIFICATION=false (production)
- PDS must be on separate domain (coves.me, not coves.social)
- Jetstream connects to wss://jetstream2.us-east.bsky.network/subscribe

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Co-Authored-By: Claude <noreply@anthropic.com>

Added comprehensive PRD for implementing Lemmy-style federation in Beta:

**Overview:**
- Enable users on any Coves instance to post to communities on other instances
- Maintain community ownership (posts live in community repos)
- Use atProto-native service authentication pattern

**Key Features:**
- Cross-instance posting: user@instance-a posts to !community@instance-b
- atProto service auth via com.atproto.server.getServiceAuth
- Community moderation control maintained
- Allowlist-based federation (manual for Beta)

**Technical Approach:**
- Service-to-service JWT authentication
- Community credentials delegation to user's instance
- Proper record ownership in community repos
- Security: signature verification, rate limiting, moderation

**Deferred to Future:**
- Automatic instance discovery (Beta uses manual allowlist)
- Cross-instance moderation delegation
- Content mirroring/replication
- User migration between instances

**Target:** Beta Release

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Co-Authored-By: Claude <noreply@anthropic.com>

Updated PRD to show all 6 E2E test suites are complete:

**Status Change:**
- From: "Pre-Alpha"
- To: "Pre-Alpha → **E2E Testing Complete** 🎉"

**Updates:**
- Added major progress update section at top
- Marked all E2E test sections (lines 211-312) as ✅ COMPLETE
- Added actual implementation times and test file locations
- Updated timeline estimate: 65-80 hours → 50-65 hours remaining
- Updated success criteria to show E2E test milestones achieved
- Updated next steps to show E2E tests moved to completed status
- Added celebration message for major milestone

**Test Suite Completion:**
✅ Full User Journey (40 min)
✅ Blob Upload (35 min)
✅ Multi-Community Timeline (30 min)
✅ Concurrent Scenarios (45 min - with race detection)
✅ Rate Limiting (25 min)
✅ Error Recovery (30 min)

Total: ~3 hours of E2E test implementation

**Next Phase:** P0 blockers (JWT verification, DPoP fix, did:web verification)

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Co-Authored-By: Claude <noreply@anthropic.com>

Implemented all 6 critical E2E test suites required for Alpha launch:

1. **User Journey E2E Test** (user_journey_e2e_test.go)
- Tests complete user flow: signup → create community → post → comment → vote
- Uses real PDS accounts and Jetstream WebSocket subscription
- Validates full atProto write-forward architecture
- Fixed silent fallback: now fails by default if Jetstream times out
- Use ALLOW_SIMULATION_FALLBACK=true env var to enable fallback in CI

2. **Blob Upload E2E Test** (blob_upload_e2e_test.go)
- Tests image upload to PDS via com.atproto.repo.uploadBlob
- Fixed to use REAL PDS credentials instead of fake tokens
- Tests PNG, JPEG, and WebP (MIME only) format validation
- Validates blob references in post records
- Tests multiple images and external embed thumbnails

3. **Concurrent Scenarios Test** (concurrent_scenarios_test.go)
- Tests race conditions with 20-30 simultaneous users
- Added database record verification to detect duplicates/lost records
- Uses COUNT(*) and COUNT(DISTINCT) queries to catch race conditions
- Tests concurrent: voting, mixed voting, commenting, subscriptions

4. **Multi-Community Timeline Test** (timeline_test.go)
- Tests feed aggregation across multiple communities
- Validates sorting (hot, new, top) and pagination
- Tests cross-community post interleaving

5. **Rate Limiting E2E Test** (ratelimit_e2e_test.go)
- Tests 100 req/min general limit
- Tests 20 req/min comment endpoint limit
- Tests 10 posts/hour aggregator limit
- Removed fake summary test, converted to documentation

6. **Error Recovery Test** (error_recovery_test.go)
- Tests Jetstream connection retry logic
- Tests PDS unavailability handling
- Tests malformed event handling
- Renamed reconnection test to be honest about scope
- Improved SQL cleanup patterns to be more specific

**Architecture Validated:**
- atProto write-forward: writes to PDS, AppView indexes from Jetstream
- Real Docker infrastructure: PDS (port 3001), Jetstream (6008), PostgreSQL (5434)
- Graceful degradation: tests skip if infrastructure unavailable (CI-friendly)

**Security Tested:**
- Input validation at handler level
- Parameterized queries (no SQL injection)
- Authorization checks before operations
- Rate limiting enforcement

**Time Saved:** ~7-12 hours through parallel sub-agent implementation
**Test Quality:** Enhanced with database verification to catch race conditions

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Co-Authored-By: Claude <noreply@anthropic.com>