feat: add Caddy web server provider

[masonjames]

Summary

Adds Caddy as a configurable web-server provider alongside Traefik.

• adds provider-neutral web-server helpers and Caddy setup/config generation
• adds Caddy route generation for dashboard, application, compose, and domain flows
• adds guarded Traefik-to-Caddy migration dry-run/apply/rollback tooling
• adds runtime upstream preflight, rollback snapshots, and migration operation locking
• adds settings UI for provider selection and Caddy migration workflow
• adds runtime Drizzle migration handling that fails closed if migrations cannot be applied

Safety model

• Traefik remains the default provider
• direct generic switching to or from Caddy is guarded; migration and rollback flows are required
• Caddy config paths are constrained to Dokploy-owned config directories
• manual Caddy fragments are detected and can block unsafe migration output conflicts
• unsupported BasicAuth hashes are blocked instead of silently downgraded
• rollback snapshots preserve Traefik resources and fail closed on missing artifacts
• migration reports are sanitized for non-admin/public surfaces

Validation

• git merge --no-commit --no-ff upstream/canary -> already up to date
• git merge --no-commit --no-ff origin/codex/caddy-web-server-v0296-clean-pr -> already up to date
• git diff --check upstream/canary..HEAD
• pnpm exec biome check over 65 changed TS/TSX/JSON files
• cd apps/dokploy && ./node_modules/.bin/tsc --noEmit --pretty false
• pnpm --filter=dokploy test --run __test__/db __test__/caddy __test__/traefik/server/update-server-config.test.ts -> 14 files / 84 tests passed
• docker run --rm caddy:2.11.3 caddy validate --help

[dosubot]

Related Knowledge

1 document with suggested updates is ready for review.

Dokploy's Space

README /dokploy/blob/canary/README.md — ⏳ Awaiting Merge

^{How did I do? Any feedback?}