fix(query): push down indexed equality + IN filters and surface DB errors

[jxom]

WHERE "orderId" = X (unquoted), WHERE "orderId" IN (X, Y), and similar multi-row joins against decoded indexed columns previously fell through to abi_uint(topic1) = N predicates with no pushdown, forcing Postgres to compute abi_uint over every selector-matching row in logs and routinely tripping the per-query statement_timeout.

The single-row = X LIMIT 1 shape worked only because the planner streamed enough rows before timing out. Cadent (and other downstream clients) had to fan multi-row joins out as N parallel single-row queries to work around the failure.

What this PR does

• Splits rewrite_filters_for_pushdown into two passes — = and IN (...) — that each rewrite a decoded-indexed-column predicate into a raw topicN = '\\x...' (or topicN IN ('\\x...', ...)) form Postgres can resolve via the logs index.
• Accepts both quoted ('17486013') and unquoted (17486013) numeric literals on the equality form.
• Leaves IN (SELECT ...) subqueries untouched (the regex's inner paren-free restriction skips them).
• Surfaces the actual Postgres DbError (severity + message) via a new format_error_chain helper instead of the opaque "db error" head string from tokio_postgres::Error::Display. Without this the underlying timeout was invisible to API clients.

Live verification (testnet)

Before:

SELECT "orderId" FROM OrderPlaced WHERE "orderId" = 17486015        -- db error
SELECT "orderId" FROM OrderPlaced WHERE "orderId" IN (17486015, …)  -- db error
SELECT "orderId" FROM OrderPlaced WHERE "orderId" BETWEEN x AND y   -- db error

After (same testnet, same data):

SELECT "orderId" FROM OrderPlaced WHERE "orderId" = 17486015        -- 1 row
SELECT "orderId" FROM OrderPlaced WHERE "orderId" IN (17486015, …)  -- N rows

Test impact

• src/query/parser.rs: added rewrite_eq_for_pushdown / rewrite_in_for_pushdown helpers + snapshots covering quoted addresses, IN-list, and unquoted numeric equality.
• src/service/mod.rs: format_error_chain + threading through sanitize_db_error.
• Full suite: 286 passed.

Downstream

Unblocks cadent#53 (GET /exchanges/:tokenA/:tokenB/orders), which joins OrderCancelled and OrderFilled by orderId IN (...) against an OrderPlaced scan window. Also cleans up the per-orderId single-row workaround currently used by the swap-feed and OHLC routes.

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Amp-Thread-ID: https://ampcode.com/threads/T-019e929b-cab4-745f-804a-8c5e03ae80dc