chore: consolidate documentation — delete status/fix/progress cruft

Before: 335 tracked .md files; top level had 14 README-like docs;
docs/ contained ~234 files, most of them auto/LLM-generated status
reports (ALL_*_COMPLETE*, *_FIX*, DEPLOYMENT_*_FINAL*, etc.).

After: 132 tracked .md files. Repo now has exactly five top-level
docs: README.md, QUICKSTART.md, RUNBOOK.md, CONTRIBUTING.md,
CHANGELOG.md (moved up from docs/).

Keeper philosophy in docs/:
- API, CCIP (ops + security + receiver/router refs), Chainlist refs,
  compliance, deployment (guides not status), database connection,
  legal compliance, metamask integration, production checklist,
  tiered-architecture implementation/setup, reusable-components plan,
  token-mechanism doc, wrap-and-bridge operational reference, plus
  docs/specs/** and docs/api/ / docs/openapi/ trees.

Deleted (git history preserves provenance):
- All 'ALL_*_COMPLETE*' / '*_FIX*' / '*_FIXED*' / '*_FINAL*' /
  '*_STATUS*' / '*_PROGRESS*' / '*_SUMMARY*' files.
- BLOCKSCOUT_*_FIX / _CRASH / _INITIALIZATION / _SCHEMA / _YAML /
  _SKIP / _NEXT_STEPS / _START_AND_BUILD / _DATABASE_CREDENTIALS
  (the last contained passwords).
- CCIP_IMPLEMENTATION_* / CCIP_CURRENT_STATUS / CCIP_GAP_*
  (gap analyses are not a sustained reference).
- NPMPLUS_CREDENTIALS_GUIDE.md (contained creds).
- LETSENCRYPT_CONFIGURATION_GUIDE.md (contained creds; will be
  re-introduced as runbook content post-secrets-scrub).
- docs/diagnostic-reports/, docs/feature-flags/ (run-time artifacts).

README.md: dead links (START_HERE, README_DEPLOYMENT, COMPLETE_DEPLOYMENT,
DEPLOYMENT_COMPLETE_FINAL) replaced with links to the five canonical
top-level docs + docs/ index.

docs/WHY_INFO_NOT_LOADING.md

@@ -1,39 +0,0 @@
-# Why Is No Explorer Data Loading?
-
-If the explorer at **https://explorer.d-bis.org** shows no stats, no blocks, and no transactions (or only "—" and "Loading..."), the **Explorer API backend is not responding**.
-
-## Root cause
-
-- The frontend loads all data from **`/api/`** (e.g. `/api/v2/stats`, `/api/v2/blocks`, `/api/v2/transactions`).
-- Nginx proxies **`/api/`** to **Blockscout** on **port 4000** (`http://127.0.0.1:4000`).
-- When Blockscout is not running or not reachable, nginx returns **502 Bad Gateway** (sometimes 503).
-- Every API request then fails, so **no info loads**.
-
-## How to fix it
-
-1. **On the Proxmox host** that runs the explorer VM (VMID 5000):
-   ```bash
-   cd /path/to/explorer-monorepo
-   bash scripts/fix-502-blockscout.sh
-   ```
-   Or from your machine if the script supports SSH:
-   ```bash
-   EXPLORER_VM_HOST=root@192.168.11.12 bash scripts/fix-502-blockscout.sh
-   ```
-
-2. **Manually** (inside the explorer VM, VMID 5000):
-   - Start PostgreSQL if used: `docker start blockscout-postgres`
-   - Start Blockscout: `cd /opt/blockscout && docker compose up -d`
-   - Ensure the Blockscout container is listening on **port 4000**.
-
-3. **Verify** the API is up:
-   ```bash
-   curl -sS -o /dev/null -w "%{http_code}" https://explorer.d-bis.org/api/v2/stats
-   ```
-   You should see `200`. If you see `502`, the backend is still down.
-
-## More detail
-
-- **502** = nginx is up but the upstream (Blockscout on port 4000) is down or unreachable.
-- Full runbook: [EXPLORER_API_ACCESS.md](./EXPLORER_API_ACCESS.md) (Fix 502, Blockscout, nginx proxy).
-- API reference: [EXPLORER_API_REFERENCE.md](./EXPLORER_API_REFERENCE.md).