chore: update Dockerfile pinned versions

[github-actions]

Dependency Version Updates

This PR updates pinned versions in the Dockerfile and synchronizes release documentation:

• OPENCHAMBER_VERSION: 1.15.0 → 1.16.0 (source: @openchamber/web)
• LEANCTX_VERSION: 3.9.7 → 3.9.8 (source: yvgude/lean-ctx)

Documentation Updates

• README badges synchronized with pinned package versions
• CHANGELOG entry prepared for the next patch release

Test Results

Integration tests passed on the updated image.

Security Scan Results

No new critical Grype findings were introduced relative to the latest published release image.

Latest Package Changes

[]

APT Updates

All packages are up to date

---

Generated automatically by the Dependency Update workflow

[tryweb]

Auto-merge approved.

Dependency Update Check workflow run #29214945354 completed successfully (2026-07-13 00:14:46Z) and the dispatched CI run #29215376957 passed all checks.

Version deltas (both safe):

• OPENCHAMBER_VERSION: 1.15.0 → 1.16.0 — minor bump, all additive (session goals, usage tracking, mobile fixes, security hardening). v1.16.0 release notes contain no breaking changes.
• LEANCTX_VERSION: 3.9.7 → 3.9.8 — patch bump (Cursor Read redirect hardening, Replace mode fixes, lean-md integration). No breaking changes.

Scope: 4 files, all auto-generated (Dockerfile ARGs, README badge, CHANGELOG, test-output.txt). Zero core code touched.

Pattern: Matches previously merged automated PRs #44 and #47.