docs: add implementation plan, ADRs, and task tracking system

- Add comprehensive 8-phase implementation plan (docs/plan.md)
- Add 28 Architecture Decision Records (docs/adr/) covering all phases
- Add task tracking system with 283+ task files (docs/stories/)
- Add task generator script for automated task file creation
- Add reference playbooks and requirements documentation

This commit establishes the complete planning foundation for the Go
Platform implementation, documenting all architectural decisions and
providing detailed task breakdown for Phases 0-8.

docs/adr/0022-cache-implementation.md

@@ -0,0 +1,56 @@
+# ADR-0022: Cache Implementation
+
+## Status
+Accepted
+
+## Context
+The platform needs caching for:
+- Performance optimization (reduce database load)
+- Frequently accessed data (user permissions, roles)
+- Session data (optional)
+- Query results
+
+Options considered:
+1. **Redis** - Industry standard, feature-rich
+2. **In-memory cache** - Simple, no external dependency
+3. **Memcached** - Simple, but less features than Redis
+4. **No cache** - Simplest, but poor performance at scale
+
+## Decision
+Use **Redis** as the primary cache with **in-memory fallback**:
+
+1. **Primary**: Redis for production
+2. **Fallback**: In-memory cache for development/testing
+3. **Interface abstraction**: `Cache` interface allows swapping implementations
+4. **Use cases**: Permission lookups, role assignments, query caching
+
+**Rationale:**
+- Industry standard, widely supported
+- Rich feature set (TTL, pub/sub, etc.)
+- Can be shared across instances (multi-instance deployments)
+- Good performance
+- Easy to abstract behind interface
+
+## Consequences
+
+### Positive
+- High performance
+- Shared across instances
+- Rich feature set
+- Easy to scale horizontally
+- Abstraction allows swapping implementations
+
+### Negative
+- Additional infrastructure dependency
+- Network latency (minimal with proper setup)
+- Need to handle Redis failures gracefully
+
+### Implementation Notes
+- Install: `github.com/redis/go-redis/v9`
+- Create `pkg/infra/cache/cache.go` interface
+- Implement `internal/infra/cache/redis_cache.go`
+- Implement `internal/infra/cache/memory_cache.go` for fallback
+- Use connection pooling
+- Handle Redis failures gracefully (fallback or error)
+- Configure TTLs appropriately (e.g., 5 minutes for permissions)
+