feat: add offline DuckLake service wiring

[weicao]

Task #71: offline DuckLake/httpfs service wiring, rebased onto current main.

Exact identity:

• head: 9b9a5ef (GitHub verified/valid, web-flow)
• parent: 2eb4143
• tree: 5543e845f3f8e6a44f178ec0d5fed3d146e8c772
• relative scope: 29 paths, no go.mod/go.sum, replication, release, tag, or image changes

The head preserves the reviewed default-off behavior, service-only S3 credential injection, connection lifecycle coverage, and fixed offline extension hashes. Existing parent-baseline connection-refused harness failures are unchanged; focused gates and compile-only checks passed.

This PR is intentionally separate from task #75 table-selection work. Do not publish or alter v0.2.0/latest from this change without the project release decision.

Known limitation

DuckDB 1.5.5 CREATE SECRET is database-global. With lake enabled, a replica connection can observe the service secret even though replica origin is zero-inject. Default-off does not create secrets and does not change current main behavior, so this does not block merging as default-off.

Until replica isolation lands in a later 0.3 follow-up: do not default-on this feature, do not add it to recommended config, and do not enable lake in environments that have replica consumers.

[weicao]

Known limitation (CTO, 2026-08-28): DuckDB 1.5.5 CREATE SECRET is database-global. With lake enabled, a replica connection can observe the service secret even though replica origin is zero-inject.

This does not block merging this PR as default-off: default-off does not create secrets and does not change current main behavior.

Until replica isolation lands in a later 0.3 follow-up:

• do not default-on this feature
• do not add it to recommended config
• do not enable lake in environments that have replica consumers

Do not retouch this head for that limitation. After merge, open a follow-up issue and assign it.

[weicao]

Cannot merge this head (9b9a5ef3).

Hosted copy-instance and Docker replica mysql/mariadb are candidate-only reds vs parent 2eb4143b: CREATE DATABASE /*!32312 IF NOT EXISTS*/ ... is rejected as service-managed. Parent those jobs are green. Replacement head must unwrap MySQL versioned comments and scan the inner SQL; ordinary CREATE DATABASE must pass.

CTO also requires rejecting CREATE PERSISTENT SECRET (and CREATE OR REPLACE PERSISTENT SECRET) on this PR before merge. One-word scanner fix; no settings/table-function sweep.

Replica-visible database-global secrets remain a known limitation and do not block default-off merge.

Need a new platform-signed head on the same parent, independent review of that exact OID, and no new reds vs parent.

[weicao]

Follow-up replacement head for the two pre-merge lexer fixes:

• 3e3be6777d290e78d6b38a0eeff118ccaa8c7f7a (parent 9b9a5ef3dae0a2794375e654be4b5f0ad441dd2b, tree cdfcb7dc831b07a27136ce6cc026dd94d49293dd)
• GitHub commit verification: verified=true, reason=valid, committer GitHub <noreply@github.com>
• Relative to the prior PR head, only catalog/sensitive_sql.go changed.

The scanner now parses MySQL /*!...*/ contents so hosted CREATE DATABASE /*!32312 IF NOT EXISTS*/ ... (including charset/encryption clauses) is allowed, while executable comments containing sensitive SQL remain rejected. CREATE PERSISTENT SECRET and CREATE OR REPLACE PERSISTENT SECRET are rejected.

Exact-head checks passed: catalog sensitive boundary, tagged backend sensitive/parser tests, tagged pgserver compile, and a disposable executable-comment probe. PR remains open for independent review.

[leon-ape]

Independent approval for exact head 3e3be67 (parent 9b9a5ef, tree cdfcb7dc831b07a27136ce6cc026dd94d49293dd). Reviewed task #80 evidence: FlightSQL concurrent/eviction/prepared-transaction checks exit 0 (log 15be53664c318bd915cb9ba98ab6551a0039b51c8d706a76827cb2aa435bfcb5), configuration default-off/redaction exit 0 (log 4b93845f8f5d23b60fa27889cb8a2b7c17c4bad67275d7f038734ece6fc3abca), and hosted backend audit-redaction pass; the local ICU failure is environment-only. Approval is limited to this exact OID and the agreed scope.