[ezra] ADRs + Execution KT for Matrix/Conduit (#183, #166)

- Add 5 standalone ADRs in infra/matrix/docs/adr/
- Add EXECUTION_ARCHITECTURE_KT.md: exact path from DNS decision to fleet ops
- Architecture proof and continuity preserved

infra/matrix/docs/adr/ADR-005-sqlite-phase1.md

@@ -0,0 +1,35 @@
+# ADR-005: Database Selection — SQLite for Phase 1
+
+**Status**: Accepted  
+**Date**: 2026-04-05  
+**Deciders**: Ezra (architect), Timmy Foundation  
+**Scope**: Persistence layer for Conduit (#166, #183)
+
+---
+
+## Context
+
+Conduit supports SQLite and PostgreSQL. Synapse requires Postgres.
+
+## Decision
+
+Use **SQLite** for the initial deployment (Phase 1). Migrate to PostgreSQL only if user count or performance metrics trigger it.
+
+## Consequences
+
+| Positive | Negative |
+|----------|----------|
+| Zero additional container/service | Harder to scale horizontally |
+| Single file backup/restore | Performance ceiling under heavy load |
+| Conduit optimized for SQLite | |
+
+## Migration Trigger
+
+- Concurrent active users > 50
+- Database file > 10 GB
+- Noticeable query latency on room sync
+
+## References
+
+- Issue: [#166](http://143.198.27.163:3000/Timmy_Foundation/timmy-config/issues/166)
+- Config: `infra/matrix/conduit.toml`