refactor: rename module to miti99bot, canonicalize AWS deploy path

Rename:
- Go module github.com/tiennm99/miti99bot-go → github.com/tiennm99/miti99bot
- CloudFormation stack miti99bot-aws-port → miti99bot
- Drop "port", "Cloud Run", "GCP", "cutover", "Phase NN" framing from
  active code and docs — project reads as canonical AWS-Lambda from now on.

AWS deploy guide + flow fix:
- New docs/deploy-aws-free-tier-guide.md — Ubuntu 24.04 ARM64 onboarding
  with project-local venv (pip awscli + sam-cli), SSM secrets via read -s,
  idempotent OIDC provider + role creation, $1 budget alarm.
- Drop sam build from the pipeline — provided.al2023 + makefile builder
  expects a Makefile in CodeUri (build/lambda/, the output dir), so the
  step always fails. sam deploy --template-file template.yaml now reads
  the raw template and zips build/lambda/ directly.
- Rollback section rewritten — use continue-update-rollback /
  cancel-update-stack / git-SHA redeploy. Drop the broken
  --use-previous-template recipe.
- DynamoDB free-tier row corrected (on-demand is 2.5M read / 1M write
  request units, not 25 RCU/WCU).

Updated:
- README.md fully rewritten (drops port/legacy framing, lists modules,
  points new users at the free-tier guide).
- aws/README.md retitled "AWS account setup", phase numbers stripped.
- Makefile / .github/workflows/deploy.yml — sam deploy flow.
- samconfig.toml — stack_name = "miti99bot".
- Go comments — Cloud Run → Lambda, Cloud Scheduler → EventBridge
  Scheduler, Cloud Logging → CloudWatch Logs.
- Struct field GCPProject → FirestoreProject (env GOOGLE_CLOUD_PROJECT
  unchanged).

Plus advisory reports under plans/reports/ from the code-reviewer +
researcher passes that informed the fixes.

Verified: go vet ./..., go build ./..., go test ./... all green.

.github/workflows/ci.yml

@@ -63,7 +63,7 @@ jobs:
         run: go build ./...
 
       - name: docker build
-        run: docker build -t miti99bot-go .
+        run: docker build -t miti99bot .
 
   iac:
     name: SAM template validate

.github/workflows/deploy.yml

@@ -19,7 +19,7 @@ jobs:
     runs-on: ubuntu-latest
     env:
       AWS_REGION: ap-southeast-1
-      STACK_NAME: miti99bot-aws-port
+      STACK_NAME: miti99bot
     steps:
       - uses: actions/checkout@v4
 
@@ -40,20 +40,17 @@ jobs:
       - name: Build Lambda binary
         run: make build-lambda
 
-      - name: SAM build
-        run: sam build
-
       - name: SAM deploy
         env:
           ALERT_EMAIL: ${{ secrets.ALERT_EMAIL }}
         run: |
           if [ -n "$ALERT_EMAIL" ]; then
-            sam deploy \
+            sam deploy --template-file template.yaml \
               --no-confirm-changeset \
               --no-fail-on-empty-changeset \
               --parameter-overrides "AlertEmail=$ALERT_EMAIL"
           else
-            sam deploy \
+            sam deploy --template-file template.yaml \
               --no-confirm-changeset \
               --no-fail-on-empty-changeset
           fi