feat: enhance webhook event data with task references and project names

[pikann]

Summary

Webhook delivery text lines previously only named the task (e.g. task "Fix login bug"), with no way to tell which project an event belonged to without cross-referencing project_id. This adds:

• Task alias — taskRef now prepends the task's human-readable alias ({task_id_prefix}-{task_number}, e.g. ABC-123) when the project has a prefix configured: task ABC-123 "Fix login bug". Falls back to the previous task "Fix login bug" format otherwise. task.created now goes through taskRef too, instead of building its own text from the activity content.
• Project name — deliver() resolves the project name once per delivery and prefixes the whole summary line with it ([Website Redesign] ...), and adds it to the structured data payload as project_name. Applies to every event, including webhook.test.

Example delivery text before/after:

- Alice updated task "Fix login bug" — title: A → B
+ [Website Redesign] Alice updated task ABC-123 "Fix login bug" — title: A → B

Test plan

• go test ./... — added TestTaskRefAndProjectNameInSummaryText, covering both the alias-present and no-prefix-fallback cases
• GOOS=wasip1 GOARCH=wasm go build -buildmode=c-shared — builds clean
• gofmt / go vet — clean