- Add ldflags in flake.nix to set version and commit hash at build time
- Pass version and commit to fang.Execute() via WithVersion and WithCommit options
- Fixes version output showing 'unknown (built from source)'
- Version now correctly displays as 'herald version 0.1.1 (hash)'

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>

- Root cause: RecordEmailSend() called while transaction tx was open
- With SetMaxOpenConns(1), this caused self-deadlock (same goroutine
trying to acquire connection it already holds)
- Solution: Added GenerateTrackingToken() and RecordEmailSendTx(tx)
that accepts transaction parameter
- Generate token before transaction, record within transaction
- Removed debug logging from email/send.go (no longer needed)

The hang occurred at scheduler/scheduler.go:412 where RecordEmailSend
tried to use db.Exec() while the transaction had the only connection
locked. SQLite's busy_timeout doesn't help with self-deadlock because
it's the same connection context.

Complete email tracking system for monitoring user engagement:

**Database & Storage:**
- Add email_sends table tracking sends, opens, bounces
- RecordEmailSend() generates unique tracking tokens
- MarkEmailOpened() records pixel impressions
- GetConfigEngagement() returns stats (sends, opens, rate, last open)
- GetInactiveConfigs() finds configs without opens
- CleanupOldSends() removes old tracking data

**Email Integration:**
- Add tracking pixel to HTML emails (1x1 transparent GIF)
- Pass tracking token through Send() -> scheduler
- Record sends in database before SMTP transmission

**Web Endpoint:**
- /t/{token}.gif serves tracking pixel
- Silently logs opens without revealing token validity
- Cache-Control headers prevent caching

**Background Jobs:**
- Weekly check for inactive configs (90 days no opens)
- Auto-deactivate configs with 3+ sends but 0 opens
- Daily cleanup of email send records >6 months
- Log auto-deactivations for transparency

**Dashboard:**
- Show engagement metrics on user profile page
- Display: sends, opens, open rate %, days since last open
- Visual indicator for inactive configs

**Configuration:**
- inactivityThreshold = 90 days
- minSendsBeforeDeactivate = 3
- emailSendsRetention = 6 months

Comprehensive tests for all tracking functionality.

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>

Enhances email deliverability and compliance:

- Add DKIM email signing support with RSA keys (PKCS1/PKCS8)
- Support both inline keys and file-based keys for flexibility
- Implement RFC 8058 one-click unsubscribe in POST handler
- Add email tracking schema (sends, opens, bounces)
- Add .gitignore rule for *.pem files

DKIM configuration via YAML or env vars:
- dkim_selector, dkim_domain required for signing
- dkim_private_key or dkim_private_key_file for key material

One-click unsubscribe detects List-Unsubscribe=One-Click POST
body and immediately deactivates without HTML response.

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>

Implemented test coverage for critical business logic:

**ratelimit package** (66.7% coverage)
- TestNew: Verifies limiter initialization
- TestAllow_SingleKey: Tests burst and rate limiting
- TestAllow_MultipleKeys: Validates independent per-key limits
- TestAllow_TokenRefill: Confirms token bucket refill behavior
- TestAllow_UpdatesLastSeen: Checks timestamp tracking
- TestCleanup: Validates stale limiter removal

**config package** (38.1% coverage)
- Parse tests: Empty input, comments, directives (email/cron/digest/inline)
- Feed parsing: With/without names, multiple feeds, complete config
- Case-insensitive directives, parseBool edge cases
- Validate tests: Email format, cron expression validation
- URL validation, missing fields, complete config validation

**store package** (42.3% coverage)
- User CRUD: GetOrCreateUser, GetUserByFingerprint, GetUserByID, DeleteUser
- Config CRUD: CreateConfig, ListConfigs, GetConfig, GetConfigByID, DeleteConfig
- Feed CRUD: CreateFeed, GetFeedsByConfig
- Seen items: MarkItemSeen, IsItemSeen, GetSeenGUIDs, CleanupOldSeenItems
- All tests use in-memory SQLite with automatic cleanup

**Test Infrastructure**
- All tests follow Go testing conventions
- Helper functions for test setup (setupTestDB)
- Use context.Background() for database operations
- Cleanup with t.Cleanup() to prevent resource leaks

**Coverage Summary**
- Total: 3 packages with tests
- 61 test cases passing
- Focus on critical business logic (parsing, validation, database, rate limiting)

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>

Implemented P3 issues #28 and #29:

**#28: Fix Inconsistent Command Help**
- Updated SSH welcome message in ssh/server.go
- Added missing 'activate <file>' and 'deactivate <file>' commands
- Now shows all 7 commands: ls, cat, rm, activate, deactivate, run, logs
- Welcome message now matches actual available commands

**#29: Align Config Defaults**
- Updated README.md line 89 to show correct 'inline' default: false
- Was incorrectly documented as 'true'
- Now matches actual code behavior in config/parse.go:27

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>

Implemented P3 issues #19, #21, #18, #33-34:

**#19: Extract Magic Numbers**
- scheduler/scheduler.go: Added 5 constants
- emailsPerMinutePerUser, emailRateBurst
- cleanupInterval, seenItemsRetention (6 months), itemMaxAge (3 months)
- minItemsForDigest (threshold for disabling inline content)
- scheduler/fetch.go: Added 2 constants
- feedFetchTimeout (30s), maxConcurrentFetch (10)
- web/handlers.go: Added 2 constants
- maxFeedItems (100), shortFingerprintLen (8)
- Replaced all hardcoded values with named constants

**#21: Remove Unused Context Parameter**
- Removed ctx parameter from store.DB.Migrate() method
- Updated main.go call site from db.Migrate(ctx) → db.Migrate()
- Context was unused since migrate() doesn't support cancellation

**#18: Error Wrapping Consistency**
- Verified all fmt.Errorf calls use "verb: %w" pattern with colon
- No changes needed - codebase already consistent

**#33-34: Clean Up Unused Code**
- Inlined getCommitHash() function into runServer()
- Standardized fingerprint shortening to 8 chars (was inconsistent 8/12)
- Used shortFingerprintLen constant for all truncation

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>

Implemented P3 issues #24, #35, and #22:

**#24: Metrics/Observability**
- Created web/metrics.go with Metrics struct using atomic counters
- Added /metrics endpoint returning JSON snapshot of system and app metrics
- Added /health endpoint for simple health checks with uptime
- Tracked: uptime, Go version, goroutines, memory (alloc/total/sys)
- Tracked: requests (total/active), emails sent, feeds fetched, items seen
- Tracked: active configs, errors total, rate limit hits

**#35: HTTP Request Logging**
- Added loggingMiddleware in web/server.go
- Logs: method, path, status code, duration (ms), remote_addr
- Uses loggingResponseWriter wrapper to capture HTTP status codes
- Tracks active requests via metrics (increment/decrement)
- Increments error counter for 5xx responses
- Middleware chain: logging → rate limiting → handlers

**#22: Standardize Logging Levels**
- Changed 23 log calls from Error → Warn in web/handlers.go
- Error reserved for critical failures (panics, failed migrations)
- Warn used for expected/recoverable failures (DB reads, template errors)
- Changed: 14 DB operations, 6 template renders, 2 response encodings, 1 delete token

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Assisted-by: Copilot: Claude Sonnet 4.5 via Crush <crush@charm.land>