1c: Add transactions + transaction_spans DB tables and queries

[ajianaz]

Parent: #231 · Blocked by: #235

Scope

Add database schema and query functions for storing and retrieving transactions.

New Tables

transactions

Column	Type	Notes
id	TEXT PK	event_id
project_id	TEXT FK→projects
name	TEXT	"POST /api/feedback"
release	TEXT	nullable
environment	TEXT	nullable
duration_ms	REAL	timestamp - start_timestamp × 1000
status	TEXT	"ok", "deadline_exceeded", etc
data	TEXT	full JSON payload
received_at	TEXT	ISO timestamp

transaction_spans

Column	Type	Notes
id	TEXT PK
transaction_id	TEXT FK→transactions
span_id	TEXT
trace_id	TEXT
parent_span_id	TEXT	nullable
op	TEXT	"db.sql.select", "http.client"
description	TEXT	nullable
start_offset_ms	REAL	relative to transaction start
duration_ms	REAL
status	TEXT	nullable
data	TEXT	JSON

Tasks

• SQLite migration file: 003_transactions.sql
• Postgres migration file: 003_transactions.sql (Postgres dialect)
• Add insert_transaction(project_id, transaction) -> Result<String>
• Add list_transactions(project_id, page, per_page, sort) -> Result<(Vec<TransactionRow>, i64)>
• Add get_transaction(id) -> Result<TransactionDetail> (with spans)
• Add get_slowest_transactions(project_id, limit) -> Result<Vec<TransactionRow>>
• Add tests: insert + retrieve round-trip
• Add tests: list with pagination

Effort: ~3 hours