refactor: replace full-node flag with explicit node-mode config

[martinconic]

Checklist

• I have read the coding guide.
• My change requires a documentation update, and I have done it.
• I have added tests to cover my changes.
• I have filled out the description and linked the related issues.

Description

Fixes #5172. The previous approach to node mode was implicit and
inconsistent: the mode was inferred from a combination of --full-node
(bool) and whether blockchain-rpc-endpoint was non-empty, which
diverged from the documented definition of modes and allowed silent
misconfigurations.

This PR introduces a single explicit --node-mode option with three
valid values: full, light, and ultra-light.

Key changes:

• NodeMode string type added to pkg/node with constants FullMode,
  LightMode, UltraLightMode; replaces FullNodeMode bool in Options
• --node-mode flag added; --full-node deprecated with a warning
  pointing to --node-mode=full
• resolveNodeMode() in start.go enforces mode requirements at startup:

  Mode	Requires
  full	swap-enable: true + blockchain-rpc-endpoint
  light	blockchain-rpc-endpoint
  ultra-light	swap-enable must be false

• isChainEnabled rewritten: no longer infers chain state from the RPC
  endpoint string — now reads directly from NodeMode
• storage-incentives-enable default corrected to false (full node only)
• chequebook-enable default corrected to false (requires swap-enable)
• All packaging yamls (bee.yaml, scoop, homebrew-amd64, homebrew-arm64)
  restructured into labelled mode-based sections

Test plan

• Start with node-mode: ultra-light and no RPC — node starts cleanly
• Start with node-mode: light, no RPC — rejected with clear error
• Start with node-mode: light + RPC — node starts in light mode
• Start with node-mode: full, no RPC — rejected with clear error
• Start with node-mode: full + RPC + swap-enable: false — rejected
• Start with node-mode: full + RPC + swap-enable: true — full node
• Start with legacy full-node: true — deprecation warning, behaves as node-mode: full
• Start with node-mode: ultra-light + swap-enable: true — rejected

AI Disclosure

• This PR contains code that has been generated by an LLM.
• I have reviewed the AI generated code thoroughly.
• I possess the technical expertise to responsibly review the code generated in this PR.

[martinconic]

Beekeeper changes are also needed