🔧[Config] Add TypeScript foundation

[maruson08]

Problem

Secure Tools had no strict TypeScript boundary for browser code, so high-risk state and lifecycle contracts remained implicit while the custom static build only copied JavaScript sources.

Result

• adds locked TypeScript tooling with strict checking and controlled, source-map-free browser emission
• migrates the Image to Text controller, output, and preview modules while preserving their existing public JavaScript paths
• keeps JavaScript, Node .mjs scripts, locale catalogs, and vendored assets in place for incremental migration
• adds build artifact guards, regression coverage, CI typechecking, and concise migration documentation

Validation

• npm ci --ignore-scripts
• npm run prepare:ocr
• npm run typecheck
• npm test
• npm run build
• node scripts/validate-build.mjs
• node tests/ocr-smoke.test.mjs
• git diff --check
• browser OCR smoke: PASS: HELLO
• browser route, legacy redirect, theme, and six-locale QA

Closes #96