[NET-14] Document Phase 1 migration and knowledge transfer

[devin-ai-integration]

Summary

Adds the Phase 1 documentation set required by Jira ticket NET-14 — "Documentation and Knowledge Transfer for Phase 1 Migration". All new files live under a top-level docs/ folder and the root README.md is updated with a banner pointing at it.

New documentation

File	Purpose
docs/README.md	Phase 1 documentation index + canonical decisions table
docs/Phase1-Migration-Guide.md	Migration overview, Strangler Fig approach, target architecture, controller / model / view / DI / static-asset patterns, end-to-end migration procedure, build/run, success criteria, explicit out-of-scope list
docs/Phase1-Configuration-Migration.md	Web.config → appsettings.json, connection strings, typed IOptions<T>, log4net → ILogger, Autofac → built-in DI, NuGet package subset, static-asset path mapping
docs/Phase1-Troubleshooting.md	Build/restore, runtime, test, CI, and local-environment issues encountered during the HomeController migration, with verbatim error messages and fixes
docs/Onboarding.md	Prereqs, clone-to-running-app walkthrough, IDE setup (VS 2022 / Rider / VS Code), netcore/ project tour, smoke-test checklist
docs/CodeReview-Guidelines.md	12-section PR review checklist (scope, migration correctness, configuration, DI, tests, code quality, formatting, docs, security, performance) + author's pre-review pass
docs/Development-Workflow.md	Branching, commit format, PR template, CI expectations, ticket linkage, working with the legacy app, Confluence mirroring, copy-paste cheat sheet
docs/training/Phase1-Training-Agenda.md	90-minute team training agenda with pre/post-session checklists, hands-on lab commands, parking-lot template, recording table

Decisions assumed (please challenge in review)

These were open questions called out in the planning comment on NET-14. I picked defensible defaults so this PR isn't blocked; if the team disagrees, the docs are easy to amend.

1. Target framework: .NET 6, per Jira epic NET-1.
2. Repo layout: netcore/ at the repo root (the layout NET-12 and NET-13 already chose).
3. Docs home: top-level docs/ — references netcore/docs/testing.md and netcore/docs/cicd.md rather than duplicating them.
4. Training format: written agenda + slide notes in repo; the live session is a team activity outside this PR. Recording link goes into the agenda's "Recording" table once held.
5. Confluence: not modified in this PR. Mirror or link once docs land on master.
6. Sign-off owner: left to PR review.

What this PR is not

• Does not touch any code under SampleWebApp/, BizLayer/, DataLayer/, ServiceLayer/, Tests/, or netcore/. Documentation only.
• Does not wait on NET-10/11/12/13 to merge. The docs reference those tickets' artifacts where applicable, with explicit notes about "if a file does not yet exist on master, it is being produced on the corresponding feature branch".
• Does not conduct the live training session — that is a team activity tracked by the acceptance criteria on the ticket.

Review & Testing Checklist for Human

Risk: green (docs-only, zero runtime impact). 3 items to confirm:

• The six assumed decisions above are acceptable. If netcore/ should be renamed (e.g. to src/ or SampleWebApp.Core/), say so — find/replace across the docs is cheap.
• The references to netcore/docs/testing.md and netcore/docs/cicd.md will resolve correctly once NET-12 and NET-13 merge. (Today they're still on feature branches, which is explicitly called out in docs/README.md.)
• Spot-check 1–2 docs (suggest docs/Phase1-Migration-Guide.md and docs/Phase1-Configuration-Migration.md) for accuracy against your own mental model of the migration.

Notes

• This PR satisfies the "Complete migration documentation available", "Documentation reviewed and approved" (pending review), and "Knowledge transfer complete" (with the agenda doc) acceptance criteria from NET-14.
• The "Team training session conducted" criterion remains a separate, post-merge activity — track the recording link in docs/training/Phase1-Training-Agenda.md.
• No CI workflows exist on master yet (NET-13 introduces them), so this PR will not run a build. That's expected.
• Closes none of the in-flight tickets — NET-14 stays In Progress until the training session is held and the ticket can move to Done.

Link to Devin session: https://app.devin.ai/sessions/dd09732f78f6403984b3c6a45865f102

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