docs(spec): the number series is configuration, not model

[delchev]

Rewrites the Document numbering section for the redesigned number: attribute:

• the intent references a series by name only - the format, scope and resetOn keys are removed
• a number is a literal prefix + the sequence zero-padded to a total width; no token grammar
• the series is a deployment-level business object: a module ships a series declaration (a requirement, like its role declarations) that provisions a missing series with default prefix/width and never overwrites an existing one; differing re-declarations of one series are an error
• per: <to-one relation> partitions a series (canonically per company - two legal entities never share a counter; identical numbers across partitions are correct)
• sequences are continuous and never auto-reset - an annual restart is an administrator setting prefix + next value
• allocating from an undeclared series is an error

Also updates the number: example in the reference card.

[delchev]

One addition to fold into this rewrite (or a follow-up): a PARTITIONED series' declaration may name its partition source — "partitions": {"table": "...", "key": "...", "label": "..."} — the physical table its partition values come from. It lets the numbering settings label each partition row by the entity's display name and list a row for every partition value BEFORE its first allocation, so an operator seeds a partition's starting number before its first document (saving such a row provisions it exactly as the first allocation would have — base shape inherited, then the edit). Identifiers are plain SQL names validated at parse; a differing cross-module re-declaration fails the artefact like a differing shape. Implemented in the reference implementation (eclipse-dirigible/dirigible#6507).