docs: reorganize tree, restore architecture + research from archive, add Phase 0 reports

Active docs/ was stub scaffolding while the real docs sat in docs/_archive/.
Restore and correct them, and record the Phase 0 work.

- docs/architecture/current.md: verified system map (from archived SYSTEM_OVERVIEW,
  9 corrections against code).
- docs/research/competitors.md: sourced competitor analysis (from archived
  PRODUCT_RESEARCH, feature matrix corrected).
- docs/decisions/ADR-002-job-application-model.md: the Job/JobApplication split.
- docs/application-discovery-report.md, docs/implementation-roadmap.md,
  docs/phase-0-foundation-report.md, docs/career-workspace-branch-assessment.md.
- Remove 10 zero-byte placeholder files that advertised content that never existed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/ux/responsive.md

@@ -0,0 +1,47 @@
+# Responsive Design
+
+## Goal
+
+Support desktop and mobile users.
+
+---
+
+# Desktop
+
+Primary experience.
+
+Optimised for:
+
+- Job management.
+- CV building.
+- Document editing.
+
+---
+
+# Tablet
+
+Support:
+
+- Dashboard.
+- Applications.
+- Profile.
+
+---
+
+# Mobile
+
+Prioritise:
+
+- Checking applications.
+- Adding jobs.
+- Follow-ups.
+
+Complex CV editing may be simplified.
+
+---
+
+# Rule
+
+Do not simply shrink desktop layouts.
+
+Design mobile experiences intentionally.