feat(integrations): sync the integrations registry into the site

[datlechin]

• integrations-sync.yml, daily and manual. fetch (read-only, no secret): resolves the latest registry release, downloads index.json, SHA256SUMS and the PNGs, runs gh release verify and gh release verify-asset per file, checks SHA256SUMS, places the files, runs IntegrationsDataTest, writes the PR body, uploads an artifact. pull-request (web-bot environment): copies only resources/data/integrations.json and public/images/integrations/, then opens or updates chore(integrations): sync registry <tag> from bot/integrations-sync.
• PR body lists added, changed and removed slugs, and active slugs without a current tagline in every locale (content/{locale}/integrations/index.json, taglines[slug]).
• No registry release yet: the scheduled run notes that and stops.
• Vendored schema/index.schema.json from TableProApp/integrations at f6c6d0f (byte copy) in tests/Support/integrations-index.v1.schema.json; opis/json-schema as a dev dependency.
• IntegrationsDataTest: schema, slug format and uniqueness, every named image present with matching sha256, size and PNG type, no other file in public/images/integrations, https-only links. Runs on the site data and on a two-entry fixture built by the registry's build.py from feat: add built-in MCP client, Shortcuts and command line entries integrations#2.
• resources/data/integrations.json: the empty index build.py produces for registry main f6c6d0f.
• IntegrationCatalog: reads and checks the index once, all() and find(), bound as a singleton. No page uses it yet.
• LICENSE-CONTENT, README and CONTRIBUTING: integration images and integrations.json are outside CC BY-NC.
• docs/deployment.md: the web bot section names the new workflow.

After merge and the first registry release: run integrations sync once by hand and check its PR starts tests.