Rebrand: Sentry -> Cairn OBS

Full rebrand across cosmetic branding, code identifiers, and
infrastructure/data-plane naming, using the supplied Cairn OBS logo
package. Cosmetic: favicon/logo swap (also closes a stale license-audit
finding -- the old favicon was SvelteKit's unreplaced scaffold logo),
new centered welcome landing page, larger/legible sidebar logo, page
titles, CLAUDE.md/README/docs prose.

Code identifiers: Go module path github.com/sentry/sentry ->
github.com/cairnobs/cairnobs across all 13 modules and ~91 files (protoc
regenerated); Rust crates sentry-agent/sentry-parser/sentry-search ->
cairnobs-*; CLI sentryctl -> cairnobsctl; Terraform provider fully
renamed (sentry_dashboard etc. -> cairnobs_dashboard, provider type,
env vars); every session/auth cookie name; agent config paths and
Windows service identity.

Deliberately preserved: the gRPC wire protocol's protobuf packages
(sentry.logs.v1, sentry.agent.v1) and their Go import directory
(proto/sentry/...) -- renaming the wire-level package would break every
currently-deployed agent binary (confirmed two real hosts, including
mail.inbuxa.com, are actively streaming through this exact contract)
until rebuilt and redeployed in lockstep with an ingest cutover. Only
the Go module path wrapping the generated code changes.

Infrastructure: every docker-compose container name (root and three
component-level compose files); the Helm chart (directory, Chart.yaml,
named-template helpers, all templates, values.yaml image repos);
Kubernetes Operator (CRD group sentry.io -> cairnobs.io, both CRD YAML
files, Go identifiers, RBAC markers); the coupled enterprise/tenantcrd
package. Caught and fixed real path-coupling bugs along the way: the
Helm chart's search/ingest volume mounts and the dev-only-credential
detection constant vs. docker-compose.yml's literal values had to move
together or a security warning would have silently stopped firing.

Data plane: Postgres database sentry_metadata -> cairnobs_metadata and
role sentry -> cairnobs; ClickHouse database sentry -> cairnobs; Kafka
topic sentry.logs.raw -> cairnobs.logs.raw and its consumer groups.
Source-level defaults, docker-compose.yml, and every migrate.sh/
provision script default updated together; already-applied migration
files left untouched per this repo's immutable-migration convention.

Verified at every layer: all 13 Go modules build/vet/test clean, both
Rust workspaces (agent, search) build/clippy/test clean, npm run check/
build clean, docker compose config validates on all four compose files.
Live-verified against a real docker stack multiple times through this
work, including a final fresh-volume run confirming the actual renamed
Postgres database/role, ClickHouse database, and Kafka topic all work
end to end with a real login and query, zero console errors.

docs/phase-3-dashboard-design.md

@@ -206,7 +206,7 @@ per panel directly, exactly the same endpoint the root query page already
 uses. This keeps `api/internal/dashboards` pure CRUD with zero
 query-execution code of its own, consistent with the project's standing
 rule that nothing duplicates `querylang`'s execution path (the same
-reason `sentryctl query` calls `/query` over HTTP instead of importing
+reason `cairnobsctl query` calls `/query` over HTTP instead of importing
 `querylang` internals). It also means panels load and error
 independently in the UI — one broken panel query doesn't fail the whole
 dashboard.
@@ -253,7 +253,7 @@ used internally, not a separate export-specific shape). `POST
 /dashboards/import` accepts that same shape and creates a new dashboard
 from it (new IDs assigned, not a literal replay of the source IDs, so
 importing into a different environment doesn't collide). This is
-deliberately the *same* JSON contract `sentryctl dashboards apply` (task
+deliberately the *same* JSON contract `cairnobsctl dashboards apply` (task
 7) consumes — "exportable/importable, Terraform-friendly" isn't a
 separate design, it's one JSON shape used from two call sites (web
 export button, CLI apply).