Plan MIL-005: ask for missing credentials and create the project .env

Add objective 9 to the Business Case (and amend objective 6 and success
criterion 1: a token may be written only to the new project's .env after a
yes), US-001.05, UC-001 extensions 2b, 9c and 9d, with the SSD, OC, SD,
DM-001, DM-002 and dictionary in step. Add the classes CredentialCollector,
EnvFileWriter and EnvFile to DCD-001 and DCD-002, and both ends'
multiplicities to every association. Restore three lines of SD-001 damaged
by an earlier edit.

Add milestone MIL-005 (9 Go/No-Go criteria, 5 tasks) and its phase in the
Project Plan. Accept the planning set and the two DCDs; reviews recorded in
RC-020 and RC-021.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

docs/artifact-registry.md

@@ -14,7 +14,7 @@ document of a type. `Primary File` may contain a glob (e.g.
 | BC | Business Case | docs/business-case.md | 002 |
 | SA | Stakeholder Analysis | docs/stakeholder-analysis.md | 002 |
 | PP | Project Plan | docs/project-plan.md | 002 |
-| MIL | Milestone / Gateway | docs/milestones/*.md | 005 |
+| MIL | Milestone / Gateway | docs/milestones/*.md | 006 |
 | US | User Story | docs/user-stories.md | 002 |
 | UC | Use Case | docs/uc-*/uc.md | 002 |
 | SSD | System Sequence Diagram | docs/uc-*/ssd.md | 002 |
@@ -24,7 +24,7 @@ document of a type. `Primary File` may contain a glob (e.g.
 | DCD | Design Class Diagram | docs/dcd.md | 003 |
 | DICT | Domain Dictionary (PO and IT terms) | docs/dictionary.md | 002 |
 | UCD | Use Case Diagram | docs/use-case-diagram.md | 002 |
-| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 020 |
+| RC | SQA Review Record | docs/sqa/reviews/rc-*.md | 022 |
 | TM | Traceability Matrix | docs/sqa/traceability-matrix.md | 002 |
 
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