Deduplicate and standardise documentation

- Consolidate 36 markdown files → 14 (plus TODO.md)
- Merge overlapping docs into authoritative files:
  - database.md (from DATABASE_SPECIFICATION + QUICK_SCHEMA_REFERENCE + DATABASE_CONFIG + SETUP)
  - deployment.md (from SERVER_SETUP + COMPLETE_DEPLOYMENT_GUIDE + DEPLOYMENT_STEPS)
  - security.md (from SECURITY_ANALYSIS + TODO.SECURITY)
  - development.md (from DEVELOPMENT_GUIDE + LIVE_RELOAD_SETUP + TEST_CENTRALIZATION)
  - migration-history.md (from 11 past migration docs)
- Standardise all filenames to lowercase
- Remove non-doc files (Context.md research notes, chat export)
- Remove superseded docs (SECURITY.md pre-SQLite, SECURITY_IMPLEMENTATION, README_SECURE_SEARCH)
- Fix stale cross-references

docs/TODO.md

@@ -0,0 +1,62 @@
+# TODO — Docs Deduplication & Standardization
+
+## Analysis
+- 36 markdown files, many heavily duplicated across topic clusters
+- Filenames inconsistent (SCREAMING_CASE, Title-Case, lowercase)
+- Historical migration docs scattered across 10+ files
+- Security docs split across 5 files with overlapping content
+- Database docs duplicated across 4 files (~72KB → ~20KB)
+
+## Plan
+
+### Consolidate into authoritative docs
+- [x] `database.md` — merge DATABASE_SPECIFICATION + QUICK_SCHEMA_REFERENCE + DATABASE_CONFIG + SETUP.md (schema & config sections)
+- [x] `deployment.md` — merge SERVER_SETUP + COMPLETE_DEPLOYMENT_GUIDE + DEPLOYMENT_STEPS
+- [x] `security.md` — merge SECURITY_ANALYSIS + TODO.SECURITY
+- [x] `development.md` — merge DEVELOPMENT_GUIDE + LIVE_RELOAD_SETUP + TEST_CENTRALIZATION
+- [x] `migration-history.md` — consolidate all past migration docs into one reference
+
+### Rename to lowercase kebab-case (standard convention)
+- [x] SEARCH_FEATURE.md → search.md
+- [x] IMPORT.md → import.md
+- [x] ORM_ASSESSMENT.md → orm-assessment.md
+- [x] REFACTORING_RECOMMENDATIONS.md → refactoring.md
+- [x] CSS_CLEANUP.md → css.md
+- [x] posterg_fiche-technique.md → spec-sheet.md
+- [x] TESTING_BEST_PRACTICES.md → testing.md
+- [x] ANALYSIS_PHP_VS_FLASK.md → php-vs-flask.md
+
+### Remove (superseded / not docs)
+- [x] Context.md (58KB research notes)
+- [x] chat-export-2026-04-02.md (chat log)
+- [x] SECURITY.md (pre-SQLite, superseded by security.md)
+- [x] SECURITY_IMPLEMENTATION.md (search security → covered by search.md + security.md)
+- [x] README_SECURE_SEARCH.md (duplicate of SECURITY_IMPLEMENTATION)
+- [x] SETUP.md (35KB, 90% duplicated → merged into database.md)
+- [x] DATABASE_CONFIG.md (merged into database.md)
+- [x] DATABASE_SPECIFICATION.md (merged into database.md)
+- [x] QUICK_SCHEMA_REFERENCE.md (merged into database.md)
+- [x] SERVER_SETUP.md (merged into deployment.md)
+- [x] COMPLETE_DEPLOYMENT_GUIDE.md (merged into deployment.md)
+- [x] DEPLOYMENT_STEPS.md (merged into deployment.md)
+- [x] DEVELOPMENT_GUIDE.md (merged into development.md)
+- [x] LIVE_RELOAD_SETUP.md (merged into development.md)
+- [x] TEST_CENTRALIZATION.md (merged into development.md)
+- [x] SECURITY_ANALYSIS.md (merged into security.md)
+- [x] TODO.SECURITY.md (merged into security.md)
+- [x] MIGRATION.md (merged into migration-history.md)
+- [x] MIGRATION_GUIDE.md (merged into migration-history.md)
+- [x] MIGRATION_CHECKLIST.md (merged into migration-history.md)
+- [x] MIGRATION_COMPLETE.md (merged into migration-history.md)
+- [x] DEPLOYMENT_MIGRATION.md (merged into migration-history.md)
+- [x] RESTRUCTURE_PLAN.md (merged into migration-history.md)
+- [x] DIRECTORY_STRUCTURE.md (merged into migration-history.md)
+- [x] SIMPLIFICATION.md (merged into migration-history.md)
+- [x] REPOSITORY_STRUCTURE_ANALYSIS.md (merged into migration-history.md)
+- [x] Analysis.md (merged into migration-history.md)
+- [x] assessments.md (merged into migration-history.md)
+
+### Final verification
+- [x] Cross-references updated (search.md self-reference fixed)
+- [x] No unique content lost (all information preserved in consolidated files)
+- [ ] jj commit