feat(notify): release v1.8.0 — Slack/Teams/Google Chat/Telegram/webhook notifications

- Add internal/notify package: best-effort release notifications to Slack, Microsoft Teams, Google Chat, Telegram, and a generic JSON webhook; every target is independently opt-in and a failed notification never fails the release
- Add notify config section (slack_webhook_url, teams_webhook_url, google_chat_webhook_url, telegram_bot_token/telegram_chat_id, webhook_url) with matching env var fallbacks; 100% coverage plus FuzzMessagePayloads
- Wire notification sending into run() — fires after tag+push (including --no-release), skipped on --no-push/--no-commit since nothing was published yet
- Document the notify section in README, Hugo docs, and .releaser.yml template; update CLAUDE.md architecture/fuzzing tables
- Also commit the Apache License 2.0 docs-site footer link (docs/hugo.toml geekdocContentLicense), left uncommitted from a prior change

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ROADMAP.md

@@ -87,4 +87,4 @@
 
 - ~~Gradle support (`build.gradle` / `build.gradle.kts`)~~ — ✓ shipped v1.6.0 (`internal/gradle`; Groovy + Kotlin DSL; multi-module via `gradle.build_files`; `--gradle` flag)
 - ~~Python `pyproject.toml` version bump (`[project].version` and `[tool.poetry].version`; single and multi-path like Maven's `pom_paths`)~~ — ✓ shipped v1.7.0 (`internal/pyproject`; PEP 621 + Poetry; `python.pyproject_tomls`; `--pyproject` flag)
-- Slack / Teams notification on release
+- ~~Slack / Teams notification on release~~ — ✓ shipped v1.8.0 (`internal/notify`; Slack, Microsoft Teams, Google Chat, Telegram, and generic webhook; each opt-in via `notify.*` config or env var; best-effort — never fails the release)