docs: fix scope naming and round-3 reviewer feedback

The docs claimed scopes are mcp:-prefixed (mcp:notes.read,
mcp:notes.write) and that the notes.* pair "covers all Nextcloud
apps". Both are false. Per @require_scopes decorators across
nextcloud_mcp_server/server/, scopes are unprefixed and per-app:
notes.read/write, talk.read/write, files.read/write,
calendar.read/write, contacts.read/write, deck.read/write,
news.read, tables.read/write, cookbook.read/write,
todo.read/write, collectives.read/write, sharing.write,
semantic.read, plus standard OIDC scopes.

Changes:

- login-flow-v2.md: replace the false 2-row "covers all apps"
  scope table with the real per-app reference (links to
  scope_authorization.discover_all_scopes() as authoritative
  source); strip mcp: prefix from intro paragraph, sequence
  diagrams, @require_scopes example, WWW-Authenticate header
  example. Also fix sticky-session keying advice per reviewer:
  route on user identity (sub claim) rather than the raw bearer
  token, since tokens rotate on refresh.
- auth-flows.md: clarify "Astrolabe (hosted UI) → MCP" matrix
  column header; strip mcp: from sequence diagram and key
  characteristics bullet; correct "issued by MCP server" to
  "issued by configured IdP" on the Login Flow v2 token.
- authentication.md: strip mcp: from the high-level diagram and
  scope-enforcement prose; cross-link to the scope reference.
- configuration.md: add NEXTCLOUD_OIDC_CLIENT_ID,
  NEXTCLOUD_OIDC_CLIENT_SECRET, and OIDC_DISCOVERY_URL to the
  Login Flow v2 vars table — these were undocumented in the
  table after the round-2 multi-IdP fix.
- running.md: drop deprecated `version: '3.8'` from compose
  snippets (Compose v2 ignores it and emits warnings).
- testing-oidc-consent.md: fix sample authorize URL and consent
  description to use real scope names instead of mcp:-prefixed
  ones (the manual test as written would have failed with
  invalid_scope).
- CLAUDE.md: replace dead links to deleted oauth-architecture.md,
  oauth-setup.md, and audience-validation-setup.md with
  login-flow-v2.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/testing-oidc-consent.md

@@ -190,7 +190,7 @@ docker compose logs -f mcp-oauth
 1. Get client_id from the JWT client JSON
 2. Visit in browser:
 ```
-http://localhost:8080/apps/oidc/authorize?client_id=YOUR_CLIENT_ID&response_type=code&redirect_uri=http://localhost:8001/oauth/callback&scope=openid+profile+email+mcp:notes.read+mcp:notes.write&state=test123
+http://localhost:8080/apps/oidc/authorize?client_id=YOUR_CLIENT_ID&response_type=code&redirect_uri=http://localhost:8001/oauth/callback&scope=openid+profile+email+notes.read+notes.write&state=test123
 ```
 
 ### 3. Expected Behavior
@@ -203,8 +203,8 @@ http://localhost:8080/apps/oidc/authorize?client_id=YOUR_CLIENT_ID&response_type
      - ✓ Basic authentication (openid) - required, cannot deselect
      - ✓ Profile information (profile)
      - ✓ Email address (email)
-     - ✓ mcp:notes.read (custom scope, shown as-is)
-     - ✓ mcp:notes.write (custom scope, shown as-is)
+     - ✓ notes.read (custom scope, shown as-is)
+     - ✓ notes.write (custom scope, shown as-is)
    - "Allow" and "Deny" buttons
 3. User selects scopes and clicks "Allow"
 4. Authorization proceeds with selected scopes