refactor: rename Ai* database identifiers to AI* (AIGOV-369) (#26327)

Adds `ai` to sqlc's `gen.go.initialisms` in `coderd/database/sqlc.yaml`
so the generated DB code follows Go's initialism convention. Adds the
matching `ai` -> `AI` case to the dbgen PascalCase helper
(`scripts/dbgen/main.go`) so the corresponding `dbmem` / mock
identifiers stay in sync. `make gen` regenerates the rest; hand-written
call sites that consume DB-generated identifiers
(`enterprise/audit/table.go`, `coderd/database/modelmethods.go`,
`enterprise/coderd/aigatewaykeys.go`, `coderd/database/dbauthz/*`, etc.)
are updated to match.

Scope is deliberately limited to the database layer:

- `coderd/rbac/*` (resource and scope generators) is untouched —
`ResourceAi*` / `ScopeAi*` constants stay on main's casing.
- `codersdk/*` (Go SDK) is untouched — `codersdk.ResourceAi*` /
`codersdk.APIKeyScopeAi*` constants stay on main's casing, so external
Go SDK consumers see no source-level break.
- `Aibridge*` identifiers (one SQL token `aibridge`, not `ai_bridge`)
are out of scope.

On-the-wire values are unchanged: enum strings, RBAC resource type
strings, API key scope strings, and JSON tags all stay the same. The
HTTP/JSON surface is unaffected.

Refs:
[AIGOV-369](https://linear.app/codercom/issue/AIGOV-369/change-ai-references-in-coderddatabasemodelsgo-to-ai)

🤖 Generated with [Coder Agents](https://coder.com)

scripts/dbgen/main.go

@@ -482,6 +482,8 @@ func nameFromSnakeCase(s string) string {
 			ret += "JWT"
 		case "idx":
 			ret += "Index"
+		case "ai":
+			ret += "AI"
 		case "api":
 			ret += "API"
 		case "uuid":