fix(deps): re-pin typescript to ^6.0.3 + ignoreDeprecations, add explicit types:node (#38)

Main red since the 2026-07-13 dev-dependencies group merge introduced
typescript ^7.0.2, which conflicts with @typescript-eslint/eslint-plugin's
peer range (still <6.1.0 as of 8.66.0) -- never exercised until today's
push. Same fix pattern as node-kaseya-quote-manager#7 / blackpoint-mcp#44 /
node-blumira (Aaron, 2026-07-22): pin typescript to ^6.0.3 + ignoreDeprecations.

That alone uncovered a second, previously-unexercised latent issue behind
the first: DTS build failed with 'Cannot find name Buffer/fetch/Response'
-- ambient @types/node globals weren't being picked up under this repo's
moduleResolution:bundler config without an explicit types:["node"] entry.
Added that too. Verified locally: build (incl DTS) + 43/43 tests passing.

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

Author: asachs01