[ENG-3233] Phase 1: GitHub App Installation Requests — Schema, Config, and Plumbing (#4312)

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## Summary

Phase 1 of the [GitHub App Installation
Requests](https://linear.app/overmind/issue/ENG-3233) project. Adds the
data foundation for tracking pending GitHub App installation requests
from non-admin org members.

### Changes

**Database (migration + schema)**
- Add 5 nullable columns to `accounts`: `github_requested_org_id`,
`github_requested_org_name`, `github_requested_at`,
`github_requested_by`, `github_requested_user_id`
- All columns have `COMMENT ON COLUMN` documentation

**SQL queries (SQLC)**
- `SetAccountGithubPendingRequest` — store pending request fields
- `ClearAccountGithubPendingRequest` — null out all pending request
fields
- `GetAccountByGithubRequestedOrgID` — lookup by org ID (for webhook
matching in Phase 3)
- `GetAccountGithubPendingRequest` — lookup by account name

**Proto (SDP)**
- Add `optional string requestedOrgName`, `optional
google.protobuf.Timestamp requestedAt`, `optional string requestedBy` to
`GithubAppInformation` (field numbers 10-12)

**Config plumbing**
- Add `GithubClientID`, `GithubClientSecret`, `GithubWebhookSecret` to
`ServerConfig`
- Add viper bindings, CLI flags, and secret redaction in
`MapFromServerConfig`
- Add 1Password references in `.devcontainer/env/op.local.env`
- Add `${localEnv:...}` passthrough in `.devcontainer/devcontainer.json`
remoteEnv

**API server behavior**
- `GetGithubAppInformation` now returns pending request fields when no
installation ID exists but a pending request is stored

**Documentation**
- Add GitHub App env vars to the API server README config table

### No user-facing behavior changes
This is pure infrastructure. Phases 2-4 build on top of this.

### Related
- Project plan: `docs/plans/github-app-installation-requests.md`
- Sentry:
[FRONTEND-NJ](https://overmindtech.sentry.io/issues/FRONTEND-NJ)
- Linear: [ENG-3233](https://linear.app/overmind/issue/ENG-3233)
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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
GitOrigin-RevId: 0586d483e565c41de6eebdd9f4e9086bfbb7f85b

Author: 2 people