v0.10.0

feat: import opencode sessions (opencodeStorageDir) (#82)

Adds opencode (v1.x storage format) as a fourth session source:

- New optional config field `opencodeStorageDir`
  (e.g. ~/.local/share/opencode/storage)
- Parser reads session info from storage/session/<projectID>/,
  message metadata from storage/message/<sessionID>/, and content
  parts from storage/part/<messageID>/; epoch-ms times converted
  to ISO 8601; sessions stored with source = 'opencode'
- `llp import` picks up the latest opencode session; `llp import-all`
  imports every opencode session across all projects
- Web UI: opencode source badge + Sessions source-filter option
- Docs: README, homepage, config.example.json updated for all four
  sources; fixed duplicated step numbering in README "How It Works"
- Bump version to 0.10.0, changelog entry

Verified against a real opencode 1.14.50 storage tree (7 sessions
imported with correct titles, models, tokens, timestamps) plus two
new unit tests on a synthetic fixture.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>