statement_timeout proconfig on bundle fns never fires; enforce via SET LOCAL

Per-function proconfig statement_timeout (mig 047 PLUTO-471, 119 PLUTO-666) does not bound the calling statement: the timer is armed at statement start with the session value (120 s for role postgres) before the function's SET applies. Measured 2026-09-20 on an isolated PG17: 3 s pg_sleep inside a function with statement_timeout='1s' completes under session 0 and 120 s; the same call after SET LOCAL statement_timeout=1000 in the same transaction is cancelled (57014); session-level 1 s also cancels (control). Prod evidence: fn_getInformesBundle 23.26 s / 11.12 s at 2026-09-19 17:01:41Z/43Z with the 4 s proconfig present, /informes 500 (appEvents 52f9443f, dd6d3c28). So the PLUTO-471 pool-cascade bound has never been in force since 2026-07-02, and 119's comment calling statement_timeout load-bearing was wrong. Fix: queryWithStatementTimeout in src/db/pool.ts (BEGIN; SET LOCAL statement_timeout=4000; call; COMMIT, ROLLBACK+release(true) on failure) used by getInformesBundle/getAlumnoDetailBundle/getPracticasBundle; 5 mocked-client tests. Consequence to state: calls between 4 s and the old 120 s that used to succeed slowly now 500 at 4 s. NOT verified: prod PG major version; cancel behaviour was measured on PG17 only. Ships with the next app push.