fix(mig 098): relax submission_code shape regex to allow digits in suffix

Mig 098 (t-paliad-209, ohm) crash-looped paliad.de prod for ~2h: §6.1
assertion regex `^[a-z_]+\.[a-z_]+\.[a-z_]+\.[a-z_]+(\..*)?$` rejects
EPA rule codes that carry the statutory rule number in the suffix —
e.g. `epa.opp.boa.r106`, `epa.grant.exa.r71_3`, `epa.opp.opd.r116`,
`epa.opp.opd.r79_further`, `epa.opp.boa.entsch2`, `epa.opp.boa.r116`.
Migration's UPDATE step succeeds against these rows; the transactional
assertion blows them up; rollback leaves the migration tracker dirty
at version 98 and the container refuses to start.

Patch: allow `[a-z_0-9]` per segment instead of `[a-z_]` in both the
SQL assertion (mig 098 §6.1) and the matching Go shape regex
(submission_codes_shape_test.go). Same change in both spots so the
runtime sanity test stays aligned with the SQL invariant.

Manual recovery already applied: forced
`paliad.paliad_schema_migrations.version` back to 97 with `dirty=false`
so the next deploy retries mig 098 from scratch against the patched
file. No data state changed (mig 098 ran inside a transaction and
fully rolled back — snapshot table, prefix UPDATE, and column rename
all reverted).

go build ./... clean. TestProceedingCodeShapeRegexStandalone green.

internal/services/submission_codes_shape_test.go

@@ -14,13 +14,15 @@ import (
 
 // submissionCodeShapeRegex is the proceeding-code-prefixed shape
 // installed by mig 098 (t-paliad-209): the proceeding's 3-segment code
-// (`^[a-z_]+\.[a-z_]+\.[a-z_]+\.`) followed by at least one suffix
-// segment (and optional further dot-separated segments). The regex
-// allows underscores so the legacy archived bucket (`_archived_…`) and
-// hand-seeded test rules (e.g. `s11a.initial`) match alongside the
-// canonical taxonomy. Mirrors the assertion in mig 098 §6.1.
+// (`^[a-z_0-9]+\.[a-z_0-9]+\.[a-z_0-9]+\.`) followed by at least one
+// suffix segment (and optional further dot-separated segments). The
+// regex allows digits so EPA suffixes like `r106` / `r71_3` / `r116`
+// (statutory rule numbers in the suffix) pass alongside canonical
+// dotted-word codes. Underscores cover the legacy archived bucket
+// (`_archived_…`) and hand-seeded test rules. Mirrors the assertion in
+// mig 098 §6.1.
 var submissionCodeShapeRegex = regexp.MustCompile(
-	`^[a-z_]+\.[a-z_]+\.[a-z_]+\.[a-z_]+(\..*)?$`)
+	`^[a-z_0-9]+\.[a-z_0-9]+\.[a-z_0-9]+\.[a-z_0-9]+(\..*)?$`)
 
 // TestSubmissionCodeShape walks every active+published row in
 // paliad.deadline_rules and asserts that submission_code matches the