feat(bindings): temporal position predicates — temporal_* named aliases

[estebanzimanyi]

Closes the user-facing tail of `temporal/034_temporal_posops` (was 0%; this brings the user-visible surface to ~100%).

New SQL surface

Time axis

Aliases for the existing `before` / `after` / `overbefore` / `overafter` named forms (the underlying MobilityDB operator tokens `<<#`, `#>>`, `&<#`, `#&>` are unreachable in DuckDB's parser):

MobilityDuck name	Routes to
`temporal_before`	`Before_*` (existing)
`temporal_after`	`After_*`
`temporal_overbefore`	`Overbefore_*`
`temporal_overafter`	`Overafter_*`

Coverage:

• temporal × temporal (every base-type pair)
• temporal × tstzspan and tstzspan × temporal

Numeric axis

Aliases for the existing `<<` / `>>` / `&<` / `&>` operators on the tnumber surface:

MobilityDuck name	Routes to
`temporal_left`	`Left_*`
`temporal_right`	`Right_*`
`temporal_overleft`	`Overleft_*`
`temporal_overright`	`Overright_*`

Coverage:

• tnumber × numspan / numspan × tnumber
• tnumber × tbox / tbox × tnumber
• tnumber × tnumber

A small `REG_POS4` macro factors out the 4-name × 4-handler block, mirroring the `REG_TOP4` macro used in PR #72 for boxops.

Tests

• `test/sql/parity/034_temporal_posops.test` — 10 assertions covering time-axis aliases, numeric-axis aliases on numspan/tbox/tnumber, and operator-vs-named equivalence.
• Full suite: 762 assertions / 14 test cases passing under `TZ=UTC`.

Coverage delta

Per the audit in PR #66:

• `temporal/034_temporal_posops`: 0/8 → 8/8 by name (100%).

Test plan

• `cmake --build . --target shell unittest` clean
• New parity test passes (10/10)
• Full suite green (762/14)

[estebanzimanyi]

Superseded by the consolidated PR branch consolidate/temporal-ops-parity. All changes from this PR are included in that branch as a single squashed commit. Please review and merge the consolidated branch instead.