Sweep all backticked + bold + table-cell + heading mentions of the
project's brand to match the PyPI distribution name and the docs domain.
Path references (`cd informix-db`, `git.supported.systems/.../informix-db`)
stay — those reference the actual Gitea repo directory which we did NOT
rename. Same with `import informix_db` (Python module name, separate
from distribution brand).
Also flip GitHub references to Gitea throughout the docs site:
- `github.com/rsp2k/informix-db/blob/main/X` → Gitea `/src/branch/main/X`
- `github.com/rsp2k/informix-db/tree/main/X` → Gitea same path
- `github.com/rsp2k/informix-db` (plain) → Gitea
- Hero "GitHub" CTA button → Gitea source URL
- Social icon: `github` → `seti:git` (generic git icon, not octocat)
Net result: zero stale GitHub references, brand consistency matches what
users `pip install`.
