feat: Complete key:value format implementation and fix tag sync

Implement complete key:value format parsing for change log entries and fix
critical tag synchronization issue from server to client.

Key Changes:

1. Shared Key:Value Parser (NEW: internal/engine/parser.go)
   - Created ParseKeyValueFormat() for both edit and sync operations
   - Supports flexible whitespace: 'key:value' and 'key: value'
   - Handles comment skipping for edit files
   - Consolidates parsing logic (DRY principle)

2. Database Triggers - Tags Support (internal/engine/database.go)
   - Added tags to track_task_create trigger
   - Added tags to track_task_update trigger
   - Tags sorted alphabetically via SQL ORDER BY
   - Format: 'tags: alpha,bravo,charlie'

3. Task Creation - Tag Update Fix (internal/engine/task.go)
   - CreateTaskWithModifier() now triggers update after adding tags
   - Ensures tags appear in change log (UPDATE entry)
   - Fixes missing tags in initial CREATE entries

4. Edit Command - Use Shared Parser (cmd/edit.go)
   - Replaced custom parseEditedFile() with shared ParseKeyValueFormat()
   - Added tag sorting in parseTags()
   - Removed ~30 lines, improved maintainability

5. Sync Client - Complete Implementation (internal/sync/client.go)
   - NEW: applyChangeDataToTask() - parses all fields from change log
   - NEW: Helper functions for status, priority, tag parsing
   - FIXED: parseChanges() - sort by timestamp+ID before grouping
   - Added parent/child task ordering (prevents FK violations)
   - Enhanced tag sync in merge loop with task reload
   - Specific validation error messages per field

Critical Bug Fix:
- When CREATE and UPDATE have same timestamp, old code kept CREATE (no tags)
- New code sorts by ID as tiebreaker, ensuring UPDATE (with tags) is used
- Verified: Server->client tag sync now works correctly

Validation:
- Description must not be empty (both edit and sync)
- Recurrence validated (not negative, max 100 years)
- All timestamps parsed correctly (Unix epoch)
- Tags sorted alphabetically in all contexts

Testing:
- Fresh pull from server: ✅ All tags present
- API-created tasks: ✅ Tags sync correctly
- Local->server->client round-trip: ✅ No data loss
- Same-second CREATE+UPDATE: ✅ Correct entry processed
- Parent/child tasks: ✅ Correct ordering

Files Changed:
- NEW: internal/engine/parser.go (+44 lines)
- Modified: internal/engine/database.go (+10 lines)
- Modified: internal/engine/task.go (+8 lines)
- Modified: cmd/edit.go (-25 lines net)
- Modified: internal/sync/client.go (+280 lines)
- Modified: srv/README.md (+1 line)

Total: +318 lines added, -25 removed, net +293 lines

This completes Phase 6: Full bidirectional sync with complete tag support.

opal-task/internal/engine/database.go

@@ -214,7 +214,12 @@ func runMigrations() error {
 						CASE WHEN NEW.wait IS NOT NULL THEN 'wait: ' || NEW.wait || CHAR(10) ELSE '' END ||
 						CASE WHEN NEW.until_date IS NOT NULL THEN 'until: ' || NEW.until_date || CHAR(10) ELSE '' END ||
 						CASE WHEN NEW.recurrence_duration IS NOT NULL THEN 'recurrence: ' || NEW.recurrence_duration || CHAR(10) ELSE '' END ||
-						CASE WHEN NEW.parent_uuid IS NOT NULL THEN 'parent_uuid: ' || NEW.parent_uuid || CHAR(10) ELSE '' END
+						CASE WHEN NEW.parent_uuid IS NOT NULL THEN 'parent_uuid: ' || NEW.parent_uuid || CHAR(10) ELSE '' END ||
+						(SELECT CASE WHEN COUNT(*) > 0 
+							THEN 'tags: ' || GROUP_CONCAT(tag, ',') || CHAR(10)
+							ELSE '' 
+						END 
+						FROM (SELECT tag FROM tags WHERE task_id = NEW.id ORDER BY tag))
 					);
 				END;
 
@@ -248,7 +253,12 @@ func runMigrations() error {
 						CASE WHEN NEW.wait IS NOT NULL THEN 'wait: ' || NEW.wait || CHAR(10) ELSE '' END ||
 						CASE WHEN NEW.until_date IS NOT NULL THEN 'until: ' || NEW.until_date || CHAR(10) ELSE '' END ||
 						CASE WHEN NEW.recurrence_duration IS NOT NULL THEN 'recurrence: ' || NEW.recurrence_duration || CHAR(10) ELSE '' END ||
-						CASE WHEN NEW.parent_uuid IS NOT NULL THEN 'parent_uuid: ' || NEW.parent_uuid || CHAR(10) ELSE '' END
+						CASE WHEN NEW.parent_uuid IS NOT NULL THEN 'parent_uuid: ' || NEW.parent_uuid || CHAR(10) ELSE '' END ||
+						(SELECT CASE WHEN COUNT(*) > 0 
+							THEN 'tags: ' || GROUP_CONCAT(tag, ',') || CHAR(10)
+							ELSE '' 
+						END 
+						FROM (SELECT tag FROM tags WHERE task_id = NEW.id ORDER BY tag))
 					);
 				END;