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/cmd/edit.go

@@ -1,10 +1,10 @@
 package cmd
 
 import (
-	"bufio"
 	"fmt"
 	"os"
 	"os/exec"
+	"sort"
 	"strings"
 	"time"
 
@@ -203,42 +203,11 @@ func generateEditableContent(task *engine.Task) string {
 
 // parseEditedFile reads and parses the modified file
 func parseEditedFile(filepath string) (map[string]string, error) {
-	file, err := os.Open(filepath)
+	content, err := os.ReadFile(filepath)
 	if err != nil {
 		return nil, fmt.Errorf("failed to open edited file: %w", err)
 	}
-	defer file.Close()
-
-	fields := make(map[string]string)
-	scanner := bufio.NewScanner(file)
-	lineNum := 0
-
-	for scanner.Scan() {
-		lineNum++
-		line := scanner.Text()
-
-		// Skip comments and empty lines
-		trimmed := strings.TrimSpace(line)
-		if trimmed == "" || strings.HasPrefix(trimmed, "#") {
-			continue
-		}
-
-		// Parse "key: value"
-		parts := strings.SplitN(line, ":", 2)
-		if len(parts) != 2 {
-			return nil, fmt.Errorf("line %d: invalid format (expected 'field: value')", lineNum)
-		}
-
-		key := strings.TrimSpace(parts[0])
-		value := strings.TrimSpace(parts[1])
-		fields[key] = value
-	}
-
-	if err := scanner.Err(); err != nil {
-		return nil, fmt.Errorf("error reading file: %w", err)
-	}
-
-	return fields, nil
+	return engine.ParseKeyValueFormat(string(content), true) // skip comments
 }
 
 // applyEditedFields applies parsed changes to task
@@ -489,6 +458,7 @@ func parseTags(s string) []string {
 			tags = append(tags, tag)
 		}
 	}
+	sort.Strings(tags) // Sort alphabetically for consistency
 	return tags
 }