docs(01): capture phase context

Phase 01: Core Infrastructure & Security
- Implementation decisions documented
- Phase boundary established

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/phases/01-core-infrastructure-security/01-CONTEXT.md

@@ -0,0 +1,69 @@
+# Phase 1: Core Infrastructure & Security - Context
+
+**Gathered:** 2026-01-25
+**Status:** Ready for planning
+
+<domain>
+## Phase Boundary
+
+Production-ready backend infrastructure with security-hardened build environment. FastAPI backend, PostgreSQL database, HTTPS, rate limiting, CSRF protection, and sandboxed ISO builds using systemd-nspawn with deterministic output.
+
+</domain>
+
+<decisions>
+## Implementation Decisions
+
+### Sandbox Strictness
+- Network access via whitelist: official Arch mirrors + our own package server
+- Private overlays can require external packages (user's SSH keys, shell configs, etc.)
+- Resource limits: generous (8GB RAM, 4 cores) — prioritize build speed over concurrent capacity
+- No direct host filesystem access (Claude's discretion on read-only cache mounts if beneficial)
+
+### Determinism Approach
+- **Critical constraint:** Same speech must produce identical ISO hash — caching depends on this
+- Fixed build locale: en_US.UTF-8 + UTC timezone for all builds
+- Package versioning and timestamp strategy: Claude's discretion based on archiso best practices
+- Cache invalidation strategy: Claude's discretion
+
+### Error Visibility
+- Friendly summary + expandable "Show full log" for power users
+- Private builds = private logs (only the triggering user can see their logs)
+- Admin access to logs requires explicit user consent ("share logs with support")
+- Log retention: 30 days
+
+### Backup & Recovery
+- Backup frequency: Claude's discretion
+- Backup retention: Claude's discretion
+- Recovery testing: Claude's discretion
+- Storage: same infrastructure (no offsite requirement for v1)
+
+### Claude's Discretion
+- Build timeout handling (soft warning vs hard kill, duration)
+- Host path access for caching (if beneficial for performance)
+- Timestamp strategy for deterministic builds (SOURCE_DATE_EPOCH or alternative)
+- Package version locking mechanism
+- Cache invalidation strategy when packages update
+- Database backup frequency and retention
+- Automated recovery testing approach
+
+</decisions>
+
+<specifics>
+## Specific Ideas
+
+- "Caching of ISOs will take up too much space if we aren't able to reproduce the same hash for an ISO with the same speech" — determinism is a hard requirement, not a nice-to-have
+- Private overlays are a real use case: user's SSH keys, default shell setup, personal configs
+
+</specifics>
+
+<deferred>
+## Deferred Ideas
+
+- Locale management tool for installed systems — "a single tool they run and get a menu to select and it does everything in the background" — future phase (user experience enhancement)
+
+</deferred>
+
+---
+
+*Phase: 01-core-infrastructure-security*
+*Context gathered: 2026-01-25*