feat: filter discovered models via includeModels/excludeModels (#27)

Per-provider glob filters (only `*`, everything else literal) let one
LiteLLM proxy be split across several OpenCode providers without
hand-maintained model lists. includeModels is evaluated first,
excludeModels always wins, and empty/omitted arrays mean no filtering.

Based on #21 by Cleverson Sacramento, with two changes for the
post-v1.0 architecture: the filter is applied inside discoverModels()
rather than at merge time, so the SWR cache and background refresh
write the same filtered view instead of the filter silently lapsing
after the first refresh; and the dead V2-schema path it also touched
no longer exists.

Co-authored-by: Cleverson Sacramento <cleverson.sacramento@gmail.com>