steps 8+9: worklog + FTS5 search

STEP 8 — Worklog:
- Migration 006: worklog_entries table (node_id, date, minutes,
  approximate, billable, summary, details)
- WorklogService: Add, Get, Update, Delete, ListByNode, SumMinutes,
  Report (text report generator with total time)
- CLI: verstak log add/list/report  (verstak log --help for usage)
- GUI tab: entries list with date/time/approx, add form with
  minutes+text+approx checkbox, total minutes counter

STEP 9 — FTS5 Search:
- FTS5 virtual table created lazily by search.Rebuild()
  (works with/without FTS5 compiled in — graceful fallback)
- SearchService: Index, Remove, Rebuild, Search (with FTS5 MATCH)
- CLI: verstak index rebuild — builds search index from node titles
- GUI search bar uses /api/search?q= (FTS5 when available,
  fallback to LIKE on node titles)

Acceptance: go build ./... pass, go test ./... pass (all packages).

internal/core/storage/migrations_006.sql.go

@@ -0,0 +1,22 @@
+package storage
+
+// migration006 — worklog_entries table.
+const migration006 = `
+CREATE TABLE IF NOT EXISTS worklog_entries (
+    id TEXT PRIMARY KEY,
+    node_id TEXT NOT NULL REFERENCES nodes(id),
+    started_at TEXT NULL,
+    ended_at TEXT NULL,
+    date TEXT NOT NULL,
+    minutes INTEGER NULL,
+    approximate INTEGER NOT NULL DEFAULT 1,
+    billable INTEGER NOT NULL DEFAULT 0,
+    summary TEXT NOT NULL,
+    details TEXT NULL,
+    created_at TEXT NOT NULL,
+    updated_at TEXT NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_worklog_node ON worklog_entries(node_id);
+CREATE INDEX IF NOT EXISTS idx_worklog_date ON worklog_entries(date);
+`

internal/core/storage/migrations_007.sql.go

@@ -0,0 +1,17 @@
+package storage
+
+// migration007 — FTS5 search index.
+// Requires SQLite compiled with FTS5 (go build -tags sqlite_fts5).
+// The migration is wrapped in a savepoint so it can be skipped on
+// SQLite builds without FTS5 (the search_index table simply won't exist,
+// and search falls back to LIKE on node titles).
+const migration007 = `
+CREATE VIRTUAL TABLE IF NOT EXISTS search_index USING fts5(
+    node_id UNINDEXED,
+    title,
+    content,
+    path,
+    tags,
+    type
+);
+`

internal/core/storage/storage.go

@@ -62,7 +62,9 @@ var migrationFiles = map[int]string{
 	3: migration003,
 	4: migration004,
 	5: migration005,
-	// 6: migration006, etc.
+	6: migration006,
+	// 7: migration007 (FTS5) — created lazily by search.Rebuild()
+	// 8: migration008, etc.
 }
 
 func (db *DB) runInitialSchema() error {